It is widely believed that color can be decomposed into a small number of component colors. Particularly, each hue can be described as a combination of a restricted set of component hues. Methods, such as color naming and hue scaling, aim at describing color in terms of the relative amount of the component hues. However, there is no consensus on the nomenclature of component hues. Moreover, the very notion of hue (not to mention component hue) is usually defined verbally rather than perceptually. In this paper, we make an attempt to operationalize such a fundamental attribute of color as hue without the use of verbal terms. Specifically, we put forth a new method--partial hue-matching--that is based on judgments of whether two colors have some hue in common. It allows a set of component hues to be established objectively, without resorting to verbal definitions. Specifically, the largest sets of color stimuli, all of which partially match each other (referred to as chromaticity classes), can be derived from the observer's partial hue-matches. A chromaticity class proves to consist of all color stimuli that contain a particular component hue. Thus, the chromaticity classes fully define the set of component hues. Using samples of Munsell papers, a few experiments on partial hue-matching were carried out with twelve inexperienced normal trichromatic observers. The results reinforce the classical notion of four component hues (yellow, blue, red, and green). Black and white (but not gray) were also found to be component colors.

A longstanding and unresolved question is how observers construct a discrete set of color categories to partition and label the continuous variations in light spectra, and how these categories might reflect the neural representation of color. We explored the properties of color naming and its relationship to color appearance by analyzing individual differences in color-naming and hue-scaling patterns, using factor analysis of individual differences to identify separate and shared processes underlying hue naming (labeling) and hue scaling (color appearance). Observers labeled the hues of 36 stimuli spanning different angles in cone-opponent space, using a set of eight terms corresponding to primary (red, green, blue, yellow) or binary (orange, purple, blue-green, yellow-green) hues. The boundaries defining different terms varied mostly independently, reflecting the influence of at least seven to eight factors. This finding is inconsistent with conventional color-opponent models in which all colors derive from the relative responses of underlying red-green and blue-yellow dimensions. Instead, color categories may reflect qualitatively distinct attributes that are free to vary with the specific spectral stimuli they label. Inter-observer differences in color naming were large and systematic, and we examined whether these differences were associated with differences in color appearance by comparing the hue naming to color percepts assessed by hue scaling measured in the same observers (from Emery et al., 2017). Variability in both tasks again depended on multiple (7 or 8) factors, with some Varimax-rotated factors specific to hue naming or hue scaling, but others common to corresponding stimuli for both judgments. The latter suggests that at least some of the differences in how individuals name or categorize color are related to differences in how the stimuli are perceived.

For the South Asian artist Francis Newton Souza (1924–2000), the color black—redolent with achromatic intensity, controverted in color theory, resonant with political potentiality—mattered. Preoccupied with the color from 1954, Souza completed a series of over fifty monochromatic black paintings in 1965. What meaning did the color have for the then London-based artist? In postwar art, the color black remained associated with infinity, spirituality, and transcendence. In contrast, situating blackness at the intersections of decolonization, Négritude, and civil rights movements tracks a contrapuntal politics and poetics of the color through Souza’s black paintings.

Gradations in skin color are a consequence of differing amounts of melanin and their varying distribution. Although many darkly pigmented skin lesions are melanocytic and can be attributed to melanin content, the color of a black lesion can also be due to blood, necrotic tissue, or exogenous pigment. The source, pattern, and distribution of the color in black lesions usually offer important insight into its etiology. This contribution reviews conditions that can take on a black color, discussing the cause of the hue and any additional impact sun exposure may have.

Vision is particularly important among the senses that humans perceive, and among them, the sense of color is called color vision. Since color blindness is characterized by color vision, color discrimination may be difficult and may interfere with daily life. Therefore, image color conversion is performed to facilitate color discrimination. However, since general color conversion does not preserve the hue of an image, the resulting image is unnatural for people with general color vision. In this research, brightness correction is performed on the equi-hue plane in the RGB space. Saturation is corrected according to the position of the pixel on the constant hue plane. This enables natural color conversion considering the color distance between pixels while preserving the hue of the image. We verify the effectiveness of the proposed method through various experiments.

In this paper, MnTiO3 powder has synthesized by solid-state method, and its color properties were also investigated. Research indicates that the L*-value of the prepared MnTiO3 powder was only 25.85, showing a pure and deep black hue, which indicates that MnTiO3 can be used as a black ceramic pigment and coating. The color mechanism of MnTiO3 pigment is attributed to the 6A1g→4A1g and 6A1g→4T2g crystal field transition of octahedral Mn2+ site. Besides, the MnTiO3 pigment exhibited outstanding tinting performance in ceramic glaze. The L*-v alue of the glaze sample with 8 wt% MnTiO3 pigment added was only 11.44, which is the minimum value reported in the literature. Moreover, the MnTiO3 pigmented coating shows an excellent solar energy utilization performance. This work demonstrates the promising application of MnTiO3 pigment in ceramic decoration and solar absorber.

Color has great importance in agriculture due to its relationship with plant pigments and therefore, plant development and biochemical changes. Due to the trichromatic vision, instruments equipped with CCD or CMOS sensor represent color with the mixture of red, green and blue signals. These values are often transformed into HSL (hue, saturation, luminance) color space. Beyond average color of the visible surface area, histograms can represent color distribution. Interpretation of distribution can be challenging due to the information shared among histograms. Hue spectra fingerprinting offers color information suitable for analysis with common chemometric methods and easy to understand. Algorithm is presented with GNU Octave code.•Hue spectra is a histogram of hue angle over the captured scene but summarizes saturation instead of number of pixels. There are peaks of important colors, while others of low saturation disappear. Neutral backgrounds such as white, black or gray, are removed without the need of segmentation.•Color changes of fruits and vegetables are represented by displacement of color peaks. Since saturation is usually changing during ripening, storage and shelf life, peaks also change their shape by means of peak value and width.

This study aims to investigate human hair color perception through two empirical studies in the context of colored hair. The preliminary study was intended to establish a numerical representation of perceptually meaningful brightness levels. It identified that the brightness level was proportional to the power of 0.766 of L*. In the visual assessment, participants (N = 47) categorized 246 hair color samples into eight color hue groups aligned with the Munsell system. Hue judgment was conducted by visually comparing dyed hair tresses with natural black hair. Based on the L*, a*, and b* values of hair tresses and visual assessments thereof, we observed the ranges of hue categories for hair color alongside the brightness levels. Additionally, the differences between the Munsell hue names and the assessment results were compared. Predominantly influenced by the dark brown hair color, the neutral orientation was shifted to the first quadrant of the a*-b* plane. The study contributes to an understanding of human hair color perception and provides insights into color categorization and labeling, especially when the context is confined.

A family of dioxythiophene (DOT)-based conjugated random copolymers, capable of reversibly switching between a neutral black and an oxidized transmissive state, are reported for electrochromic (EC) applications. By replacing 3,4-ethylenedioxythiophene (EDOT) in the previous generation of a core donor–acceptor–donor (D–A–D) terheterocycle with a methyl-alkylated 3,4-propylenedioxythiophene (ProDOT), we enhance the solubility of precursors and monomers in this new generation of broadly absorbing electrochromic polymers (ECPs). By adjusting the newly designed terheterocycle monomer feed ratio, we obtain three polymers with varying hues of color neutrality (a* and b* < ±10) throughout the entire switching voltage range and with integrated contrasts 45–49% throughout the visible region (380–700 nm). The a* values of the polymers ranged between −8 (green hue) and +5 (red hue), with their b* values ranging between −4 and −7 (blue hue) in their neutral states; additionally, the a* and b* values are all below ±8 i...

Color intensity projections (CIP) have been shown to improve the visualisation of greyscale angiography images by combining greyscale images into a single color image. A key property of the combined CIP image is the encoding of the arrival time information from greyscale images into the hue of the color in the CIP image. A few minor improvements to the calculation of the CIP image are introduced that substantially improve the quality of the visualisation. One improvement is interpolating of the greyscale images in time before calculation of the CIP image. A second is the use of hue cycling - where the hue of the color is cycled through more than once in an image. The hue cycling allows the variation of the hue to be concentrated in structures of interest. If there is a zero time point hue cycling can be applied after zero time and before zero time can be indicated by greyscale. If there is an end time point hue cycling can be applied before the end time and pixels can be set to black after the end time. An angiogram of a brain is used to demonstrate the substantial improvements hue cycling brings to CIP images. A third improvement is the use of maximum intensity projection for 2D rendering of a 3D CIP image volume. A fourth improvement allowing interpreters to interactively adjust the phase of the hue via standard contrast - brightness controls using lookup tables. Other potential applications of CIP are also mentioned.