The new BLMA searchlight signals use individual red, yellow and green LEDs whereas the Sunrise signals used a single bipolar (red/green) LED. Given the fact that you are in N scale I would think replacing the LED would be extremely challenging as Guy said. Although you'll be throwing away a nice, albeit non-functional, signal I would also suggest just buying a new signal. BLMA's N scale signals should be on the market "soon."
Chuck
Logic Rail Technologies
Good Luck with the project. Sunrise made great SP style searchlight signals. I bought as many as I could get my hands on (HO scale) before he went out of business. I burnt up one of mine...It is now a static model. There is a new company on the scene, BLMA. They might be able to help you out. Even if you get the LED I would think that changing it out would be a real bear and it might be more sane to buy a replacement signal on Ebay or maybe from BLMA.
BLMA link
http://www.blmamodels.com/cgi-bin/webstore/shop.cgi?c=start.htm&t=main.index.htm&storeid=1&ud=CAcABAEMAQEDBxQUEBEcHAACBQYDCA0ECQkTEQAA
Guy
see stuff at: the Willoughby Line Site
Anyone know what LEDs sunrise used in their N scale signals?Sunrise is out of business now and I need to replace a couple of LEDs.They are Bi Coloured LEDs used in their search light signals.
Thanks