Traditional 120 volt pool lights are very simple in their design. They have a light socket, a standard bulb (incandescent or halogen) and an overheat sensor. They typically come with a clear lens, but are available with blue lenses. You can also get colored light covers that snap on the front of the light.
Be careful. These are cheaper than installing a new LED light, but if the old light fixture starts to leak, the bulb will be ruined and is not covered by any manufacturer’s warranty.
If the bulb burns out, it must be replaced. It is also a good idea to replace the gasket at this time, so you get a good seal on the fixture.
The process is fairly simple: Turn off the power, remove the set screw that attaches the fixture in the niche, pull the light up on the deck, disassemble the light, replace the bulb and gasket and put it back in the pool.
If you are changing a halogen bulb, it is important that you not touch the bulb with your fingers because oils and other contaminants from your fingers will cause the bulb to blow rather quickly.
If you have a standard 120 volt light in your pool or spa, you MUST have ground fault protection (GFCI) and you need to test it regularly.
GFCI protection can fail, especially the GFCI receptacles. Try to keep anyone from plugging high-amp power tools into these receptacles because you don’t want to risk fusing the contacts and losing the GFCI protection.