I know someone mentioned doing exactly that in the past. I do not remember who it was (have an idea but not sure) but to answer, yes it has been done.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Yes, I used the ultra-superbright radioshack red LEDs, 4 of them on each side on my SD. Any less and you'll have to throw in resistors. Seems to work fine, bright enough for me but probably not as bright as the old bulbs on max.

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Do you happen to have a pic of what it looks like red?

A Word of Caution:
When upgrading to LED in the instrument cluster, DO NOT replace the alternator light with an LED bulb.
The charging system needs this bulb to be a free flow load (no diodes) and an LED is simply that. a diode. With LED, the alternator does not get the signal to excite when the ignition is turned on.
My 2 cents

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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FACEBOOK: PANZER450

This was my old setup, slightly different than what I have now. I did take pictures though.
Boxy Brown, the groove machine

That setup was using automotive LEDs, which were not as bright. I later switched to the radioshack LEDs and soldered it all together with better results--sorry I don't have pictures of that and my SD is currently in another state but you can get the idea of what the red looks like. I think it is pretty bad ass myself

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

I had red LED in the SD when I was driving it, and it looked really cool, like military night lighting, but it was hard to get a read of the gauges and speedometer "at-a-glance" so I went back to white LED. I also had LED for everything else except for aforementioned ALT light, and the high beam. the High beam indicator was REALLY bright, being it was a blue LED. TOO bright.

__________________
RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

____________________________
FACEBOOK: PANZER450

Id like to see some photos of climate control LEDs. And perhaps a model name and LED p/n that fit into each location.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Red looks good. I'll have to give it some thought.

That turned out great! Thanks for the link.

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Brad
1981 300TD - daily driver
1963 Chevy II
2001 F-250 7.3 Power Stroke