I definitely don't think I've seen that at all!Forearm textures are located on their own unique texture map. If I haven't uploaded this file to the Archive, let me know and I'll be sure to update accordingly. However, for your own benefit, here's the file you'll want.
I have the texture pack that I also downloaded a while back, and the forearms are not in it. Just the attachments for everything and the helmets.
I couldn't get it to appear in my extracts either, and mine don't look colorful like yours do. Do you have one for the undersuit?
I have the whited out diffuse and the purple zbump, but that's all. I made that grey one by overlaying the two and taking the color saturation out of the zbump.