lights do not realy "burn out". They do shift spectrum over time (toward the lower or "yellow" end) and this is why they need to be replaced. If they are not coming on, turn your attention to the ballast. As far as color goes...it is up to you. If I am not mistaken, the Aquatraders stock MH
bulbs are 20K. This is more on the higher end, or blue/purple portion of the light spectrum. Replacing them with new actinics is a good option for presentation. If you find the tank too "blue" for your liking you can look at 50/50 bulbs. Most corals demostrate the best growth in the 6700K to 7900K light range. If you lite your tank soley in this spectrum it will appear very yellow. this is why actinic suppliments are used. For appearence purposes, I like a 10k or 14k MH
with actinic suppliments. I recently replaced both the CF
bulbs in my Odyssea fixture with bulbs from Aquatraders. I went with 10K.