I'm not a 'car' modeller but my son has a 1/24 AMT kit he's building (TFATF 1995 Mitsibushi Eclipse) and asked me if he could use some of my paints and the outcome may be of interest to your branch of our hobby.
Trouble is he can't decide what colour the body should be (He doesn't want to finish it as the box art).
Anyway I wondered what would happen if I mixed Tamiya X-32 Titanium with X-23 Clear Blue and got a metallic blue colour (I kind of thought this would be the case). So then I tried X-32 and X-26 Clear Orange which resulted in a very fine 'pale gold'. If you mix all three paints a metallic green appeares!
I've no Clear Red so I can't experiment with that but by varing paint ratios (and paints, Tamiya do more than one 'silver' type of paint XF-16 for instance), you could get some decent (and cheap) custom finishes.
Someone out there has probable done this before, but I thought I'd share ...Just in case
TTFN
Tom











