What are the actual Multigrade colors?

[AgX]

I didn't even think of the effect of IR light, but my test prints are very sharp so far so hoping it's not an issue. Step wedge testing is also a great idea, but I'm time poor right now.

Photographic papers are not sensitive to IR.

 

[Craig]

To obtain maximum contrast, i.e. grade 5, you want to cut off any light above approximately 470nm. The low contrast is green, in the 520-530nm wavelength. LED's are not single spectrum emitters, they have a peak, but also significant spread. Thus if your blue light is a bit sloppy and spreads into the green spectrum in the 470-500nm range you will never be able to develop maximum contrast.

Ideally for split grade you want the hard exposure to be in the 440-450nm wavelength and low contrast to be in the 520-530 nm wavelength. Any light outside these wavelengths should be removed. You can't specify these by hue and saturation, you need to know the spectral output of your light source.