[Ashlandchris]

if using rattle cans, Tamiya sprays have a colour chart

I'd say that TS19 (metallic blue - bottom row, 4th from left)) is what you are after (but haven't used it so can't say for certain)

Certainly, the backing colour can influence the paint colour and the advice above sounds pretty good. Only comment would be the put a few thin coats so you don't get unevenness in the shade, but then back it to darken, lighten or simply to seal!!