Probably more of an urban fantasy sort of thing.

If we’re going “classical elements”: Black is earth, cyan is water, yellow is fire, and magenta is air/sunlight because plants need magenta light? 83.89

If we’re assigning numbers to colors: K = 0 & M = 2, don’t know about the other ones.

Cyan:

Magenta:

Yellow:

Key:

Do people get one color or two colors? Probably just one, but cooperative casting should be common. Combining any two of CMY gets obvious results. CK = teal, MK = purple, YK = …beige? olive? bronze? brass?

You probably get magic around 20 or so? This shouldn’t be a hard limit, but I don’t want people to be born with it. People should definitely be able to choose their magic type. Also, it should be rare. Do we have magical creatures? Possible magic-acquisition method is “finding (pretty minor) magical creatures and doing nice things for them such that they choose to give you their magic upon death”. I don’t want the existence of magic itself to be secret.

“If you want to solve a problem… {tell a cyan mage you’ll be impressed when they solve it,
- find a yellowmage likely to consider it a problem according to their values, talk to them, and wait a year - .”