(here's a pic from my helmet for reference. The yellows on the back are the base color. I plan to weather it a bit (cause I like it dirty) but it seems to work fine.)
I'm working on the rear part of my helmet, particularly the yellow highlights etc. Well I mixed a color, dabbed it around, etc. This took about 45 minutes. Then I go in with the x-acto to clean up the edges and make it look more random and etched etc and what do I find out? If you just scratch through to the base resin color it looks almost dead-on! The frickin' helmet is a subdued yellow! I'm such an idiot.
Mask it off, scratch through to the base, whatever. It's an excellent color and saves trying to mix it up.
Hope this helps,