As some of you know, the white needles will light up whatever color the backlight of the gauges are.

What I want to know: Has anyone tried to change the color of the needles without painting the outside? Couldn't you paint the clear plastic that the light shines through on the underside and it would change the illumination of the needle?

I'd like to try this or see if anyone already has

 

I bet you could paint the underside or even top of the needles with something like glass paint or duplicolor metalcast spray paint.
Using white led's behind them should let them glow whatever color the paint is... might need to sand off the white first, but I don't see why it wouldn't work.