typically the green is actually an underlay, ie a transparent green film behind the letters and numbers or it paint behind an opaque white. if it is in fact an underlay you can remove it and use red tint film found at most parts stores. when i used to tune vws a lot of guys would do this for the full on euro colour code everything look. now if its paint you have to lightly may i please stress lightly sand the paint off with somewhere around 600 grit or higher its very thin, then repaint with the color you desire. but only one thin coat maybe 2 or the light won't shine through. use a flash light behind the gauges to determine when enough is enough and i don't mean a 6 d cell mag light. now if it is a colored bulb... i'm not going there lol. this is just from my experiences may not be what mb uses never took one apart before hope that's some help!