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1. (Astronomy) astronomy the difference between the apparent magnitude of a star measured in one standard waveband and in a longer standard waveband, indicating its colour and temperature
2. (Geological Science) geology the sum of the dark or coloured minerals of a rock, expressed as a percentage of the total minerals
3. (Chemistry) chem physics a systematic arrangement of colours according to their hue, saturation, and brightness
4. (General Physics) chem physics a systematic arrangement of colours according to their hue, saturation, and brightness