painting aluminium components

Hey guys, I'm doing a engine rebuild and I just finished painting and oven curing the VHT paint, the paint job looked great....except for one minor detail....I hate the color:doh: can I paint over the cured VHT or do I have to strip it all off:banghead:

On my last build I painted the barrels black. I put a lot of time into the preparation and the engine looked pretty good but after a few weeks lots of small lumps appeared under the paint. Does anyone have any tips on painting the barrels to prevent this happening. I am also painting wheel rims...