How to calculate the k (colour temp) of a combination of bulbs?

[kien]

Originally Posted by Magickiwi

I think a Fuji purple is 420nm.

I have no idea what the wavelength of the fiji purple bulb is either. If I recall correctly that bulb's spectral graph peaks in two places, the mid 400s and down in the mid 600s. No clue what its over all wavelength would be. I'd imagine that makes figuring its colour temperature even harder.