One of my cruise bulbs went out a few years back and I replaced it with an LED and series resistor. Wish I could remember specifics but what I do remember and is typical for what I'd do is:
5mm 100mW standard/encapsulated leaded LED that I already had, with the dome sanded down flat then polished to be optically clear again. That spreads out the light. The dome it started with is effectively a molded plastic focal lens. If you're not as cheap as me and buying LEDs, you could use something like the following instead of sanding down what you have:
http://shop.rc-electronic.com/LIGHT...p=k_emcotec_e&a=article&ProdNr=OPT4200&p=2093 It's just an example of one with omni-directional light.
1/8W resistor, roughly 1.2kOhm with multimeter probing to determine polarity of the power going to the bulb. I wrote 1.2k and 100mW LED but this under-drives the LED for good life without heatsinking, especially using low quality generic LED which may not really be 100mW despite such a rating.
It was soldered to the PCB.
I might have used a hair dryer to soften up the plastic before disassembling the switch module to lessen chances of it cracking.
I used a white LED and can't now remember if the colored condom fit on it or if I used a sharpie marker to color it. You could just buy a colored LED then calculate the different resistor value needed for it but both of the common colors, blue and green, have about the same forward voltage as white so a 1.2kOhm resistor should work for any of the 3 colors.
If I ever have to do another of those I'll snap some pictures.
