The DIN 54231:2005 and ISO 16373-2:2014 standard methods recommend the application of HPLC separations and detection by either diode array (HPLC–DAD) or mass spectrometric detectors (LC–MS or LC–MS/MS) for the evaluation of mass concentration of colorants (y ≥ 1.0 µg/mL) in textile sample extracts. The present investigation reports for the first time that the LC–MS/MS method has low accuracy for most of textile colorants if the recommended calibration range of the standard methods (1.0 µg/mL to 20 µg/mL or 5.0 µg/mL to 50 µg/mL) is used. The present paper reports that the quantification of mass concentration of colorants in textile extract by the LC–MS/MS method does not match with the quantification by the HPLC–DAD method, which has fit-for-purpose linearity and accuracy in the ranges mentioned above. A systematic study of the MS/MS method was performed to prepare real and spiked samples for quantifying mass concentration of colorants (y ≤ 1.0 µg/mL) in textile extracts for compounds having LOQ ≤ 1.0 mg/kg. The results obtained could match with the quantification by the HPLC–DAD method. A lower calibration range was needed to quantify the dyes in the diluted sample extracts in which the background matrix constituents had lower influence on the quantification. Significantly, the LC–MS/MS method utilizing sample dilution and lower calibration range was validated and then used to proficiency test (PT) samples with success. Furthermore, the evaluation of mass fraction of disperse yellow 3 in PT sample by exact-matching double isotope dilution mass spectrometry was also performed. The strategy presented herein to quantify a wide range of colorants using the LC–MS/MS method could improve the reproducibility of analyzing colorants using protocols of standard recommendations.