Unfortunately there is nothing you can do than get new armor, or paint it.
I have a CAP High Gloss HIPS helmet that is awesome, but it makesmy FX armor look almost pink!!! I hated it so I bought new shoulders, chest, biceps, and back in High Gloss HIPS to blend in to the rest of my FX. -And it looks great.
IMHO, I love the FX ABS, it's very durable, but the color doesn't match any other plastic particularly well.
****** The helmets didn't match the rest of the armor in the films either..... So, you might as well not worry about it.