I'm curious what material people have used to turn their halogen landscape uplights red? I think a simple film would work, but the bulbs put off so much heat I would assume you need some specific heat resistant material.
Buy some professional lighting gel sheets. Rosco 25 (red) is a good choice.
Depending on the size and number of your lights, one sheet might do. This is how theaters and film lighting is colored. Those lights burn very hot and the color sheets are designed to last next to high temperatures. You can cut the sheet into the sizes you'll need.
You will have to find a way for the gels to be used without their actually touching the lights. I like to use an appropriately sized can with both ends opened and placed over the fixture. Remember to cut some vent holes behind the light. Simply wire, tape, or tie the gel in place. .. what works best will depend on the heat factor. Even better would be to cut a slice in the can almost completely around the circumference- directly below the rim- and simply slip the gel into the slot.
I love using professional grade lighting gels because I can easily and quickly change colors and don't have to buy colored bulbs. If you take care of it, lighting gel will last for ages.
eta: Gel lighting sheets are usually 20" x 25" and cost about $7 each.
We use the colored LED spots from Minions Web. They dont get hot and they save so much in the electric bill They are about $35 but last forever and we use the red and blue wash together and it looks really great.. We stick them in the regular outdoor spot holders ~ Pat