Andrew,
Yes, you can change the default lighting by changing some values in the panel.cfg. I'm not at my PC right now, but from memory if you look at the bottom of the panel.cfg, there will be 3 lines (I think) that include the names 'color' and 'luminosity', followed by three numbers - these are Red, Green, Blue values. The 'color' figures define the colour cast of the panel in the dark, and the luminosity figures define a colour illumination that you would like your gauges to show up as.
I'd give you my values for a subtle yellow, but - yep, not at my PC!
Play around with the values (or see what they look like on Photoshop or similar) and see what comes out.
