The objective signal-to-noise performance of component colour video signals is analysed in this paper for FM and AM-VSB video transmission systems. In the analysis, the effect of splitting the composite video signal into its components, by subcarrier demodulation and colour decoding, is taken into consideration. The effect of non linearity of the display is also included in the analysis. An expression for objective component signal-to-noise ratio is derived for both the transmission systems. A relationship between the conventional composite video SNR and the component video SNR is established. Effective noise transfer, between the input and various stages of video signal processing, is discussed in detail. Noise spectral density analysis, for fully saturated primary colours, is evaluated quantitatively for a PAL-I video system. Finally, SNR performance of various hues at constant luminance is evaluated, and the results obtained are compared with the subjective noise visibility tests first carried out in 1957.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>