I did only make good experience with RIT powder dye so far - i use half to a whole pack in about 1,5 l of water, let it simmer not boil. I usually dye for about 30 minutes, rinse with warm water, put them into a vinegar bath and then rinse with tap water. Until now no rubbing off/ stained skin/clothing.
This one for example was jelly and light blue like the 2 in the background.
It´s with Sjors now, so you will have to ask him if the dye bleeds or the resin looks like it once was coloured differently.
Did you clean the resin parts before dyeing? The button will not dye, it´s not resin but (ABS?) plastic.
PS: I checked my apares box - the 6900 case i have has no light button anymore, sorry. I believe i have a DW 004 body and will check if the light buttons are interchangeable.