I understand that the Dulux paint colour codes are based on the NCS colour system. I'd like to convert between this and the RGB/CMY systems, so as to be able, for example, to identify the Dulux colour most closely matching a given 3-byte hex code (e.g. in CMY, primary magenta as 00FF00).
I have been unable to find the mathematical specification of the NCS.
I have read the material at the NCS website and would be grateful if someone could tell me whether
a) the definitions of the elementary hues R, Y, etc. in NCS are the same as in CMY and RGB?
b) the gradation between two neighbouring elementary colours, e.g. R and Y, is linear (in CMY terms)?
c) a colour such as S 2030-Y90R can be made by subtractively mixing - 20% black (255/255/255 in CMY) - 30% of the hue defined by Y90R - 50% white (0/0/0 in CMY)?
If the answer to each of these questions is yes, conversion is simple, but I suspect there is more to it than this. I know that some NCS codes do not exist, i.e. some spaces in triangles in the NCS colour atlas for given hues are left blank. I am not sure whether this is because the colours are imaginary or just because the required pigments do not exist.
If there *is* more to it than this, could someone post sufficient information to allow conversion between NCS and CMY (and therefore RGB), given standard illumination conditions? If the answer to c) above is 'yes', all I need is a formula for converting between the two codes for a given hue.
Obviously a formula for converting between NCS and any colour system from which I can get to RGB will be just as good! :)
Failing this, does anyone know the RGB codes for the elementary colours (red, green, blue, yellow) used in NCS? Or the NCS codes for the primary colours in RGB or CMY? I have looked on loads of colour conversion sites, but haven't been able to find even this information, anywhere!
Many thanks in advance for help with this.
Yours sincerely,
Chris