I found this post about getting the yellow out of the vintage figures like storm shadow, but i didnt want to put the link up here without permission, its very good post and helpfull, i will be trying it this weekend to make sure it works! but if i get the permission to post the link then i will.
basicly, you put the figure in a jar with the lid on, but you have to take it apart, no screws, no o-ring or t-bar, put the parts and 30% peroxide in the jar lid on, and put it in direct sunlight for a few hours.