this is just a guess but he probably just threw some paint on it... Carefull not to get the black and blue parts mixed and then just sanded the top of it clean...
you can also just spray it diff colors being careful, and then take a shop towel stretched tight across a paint stick or something, wet it with lacquer thinner, and wipe the excess paint off leaving the metal to be polished
Polish the plate first then tape off each part one at a time and paint them. I use my finger nail to take off the paint on the high areas. Then use Q-tips and denatured alcohol to clean up the plate. Last it gets Mothers polish.
Painting the dot would be hard but it could be done. I'm working on a stock 5.0 plate now it will have a red 5.0 with a black dot. I'll post it when it is done.