Not quite true, it's about the colour that the wall reflects and emits.

In case you have not much UV-light, there will not be much blue emittance either.
But many darkrooms are used for lighted work too, as critical proof of prints, including colour prints. What would be the idea behind installing a high quality daylight-TL lighting when you add additional blue to the room, and the print to be examined.

Maybe this all is academic. But so might be this whole thread.