I just got a set of Brembos and need to touch up the paint also. I've done some research and here's some good info:
Via this forum thread, a hobby model paint brand Humbrol makes a #54 paint which matches perfectly. You can get it only on ebay as it's European and every shop I contacted in Europe won't ship paint, unless you find a local hobby shop in the US that has or can get it.
I found a color match system for US model paints and I have a local hobby shop ordering me a few bottles of Testors brand 1782 Bright Brass. I'll post pics of how it works.
My car is mainly for AutoX and the track so I hope the temps don't ruin the paint right away. From reading on that forum link above, some people on there track their cars also and had good luck with the paint not burning or fading for a long time.