So I was doing some experimentation this weekend with a some Buzzer 25th legs for my BA v.20 JCW figure and decided I'd toss my extra Stalker into the blue dye bath as well. It looks like the whole torso section doesn't take dye very well. After him sitting in there for a few hours, it accepted just a bit of the dark blue dye. The thighs were a close second on the dye blocking. The softer plastic in the arms and lower legs took it like a champ. The knees soaked it up the most. Just thought I'd post my findings for those for later tries.
*The actual figure is a bit darker than what came out from the pic. His knees are almost black and the arms are close to it as well.