FROM HUE DESIGN DOCS
#Conversion between RGB and xy in the CIE 1931 colorspace for hue The conversion between RGB and xy in the CIE 1931 colorspace is not something Philips invented, but we have an optimized conversion for our different light types, like hue bulbs and LivingColors. It is important to differentiate between the various light types, because they do not all support the same color gamut. For example, the hue bulbs are very good at showing nice whites, while the LivingColors are generally a bit better at colors, like green and cyan.