I removed the A/C switch from my 2002 Hyundai Accent. It turns out that two small 3mm diameter 12V incandescent bulbs with wire leads are used for illuminating the word "A/C" and for separately illuminating the green indicator which indicates when the A/C system is turned on. The green tint comes from a separate green filter. Both bulbs actually are white. I am not sure what wattage these tiny 12V bulbs are, but one bulb is slightly longer than the other.
Following is a photo showing my car's A/C switch, the bulbs, and the bulb holders. The bulb leads are simply wrapped around two posts on the bulb holders and then any excess wire is snipped off. To remove the bulb holders, use a small screwdriver to rotate them about 20 degrees counterclockwise until they stop. Then use a really small jewelers flat head screwdriver to lift the bulb holders out of their sockets in the switch.
(IMG:
http://i288.photobucket.com/albums/ll200/MEM-TEK/2002_Hyundai_Accent_AC_Switch_Bulbs.jpg)
Following are links to two sources which I found for some 3mm diameter 12V bulbs with wire leads. One source has 35mA bulbs, and the other source has 50mA bulbs which would be a bit brighter. I am going to order two of each, figuring that one or the other should provide the ideal brightness.
12V 35mA Micro Lamp 0.12" 3mm Dia.12V 50mA Micro Lamp .6W 3mm Dia.