Yes, to some degree you can mix, but it's going to be a
wash of light and very dependant upon the location of the fixtures as to what it's going to look like or what's covered. That will get you lots of colors in a very
broad wash, but little control over them. Also since the filaments are large, changing between them will not be that quick as per a flicker between colors. Add to this that in mixing you will have to account for amber
shift - the light when dimmed to get colorations will get an amber color to it in both washing out the punch of pure colors and make it difficult to mix. Primary colors would be the key and hot
color temperature on the lamps, perhaps even with some color correcting
gel might have a good
effect. Should you have budget for re-lamping, matching the wattage to the
intensity would be the best plan. Primary color red would have a much lower light transmission than blue or green thus you might need a higher wattage lamp on the red
cyc than the other ones also to get the same output.
Can be done, and it can look really good but if it's more of an
effect you are looking for, and a
quick change between colors in localized areas I don't know if strips would be as useful. Lots of time to tinker is the best plan. More an overall coloration for a few colors at
preset levels especially on a
cyc or overhead
wash of the
stage, if not
foot lights. If they are not
RSC/double ended types you can stand them up as side lights also, but double ended ones are not usable at more than a 15 degree angle.