STOOF,
What type of cockpit is it ? WWII , Modern, Sci-Fi ? Look at the background color of the panel. Something that may act as a shadow around the gauges. A color that is a shade darker that the panel. You may want to use a Black or a raw Umber/Sepia wash. It would give it that subtle difference in color & not look out of place, as long as the gauge bezels are black. IMHO
* I don't model aircraft. So I can't answer difinitively on the colors of the panels. I'm just an Armor Nerd Herder ;D