Prior to owning an Ilford 500 head on a Durst 138 I regularly printed graded papers using an ordinary "blue" cold light head. I read somewhere that using green light (low contrast with Multigrade papers) with graded papers would produce a slightly softer contrast version than using blue light ( high contrast with Multigrade papers) I found this to be true, at least with the Agfa papers that I was using.

I've never tried it with the 500 Head as I use the Multi graded papers most recently as opposed to older graded versions. Seemed to have a slightly greater effect with cold tone papers vs warm tone papers.

Cheers