So the only way I know while in build mode to change a light to the desired light color is go to live mode, put a Sim on the lot, and then manually change the light, and if you then go back into build mode and see that you've forgotten to change a light, you must repeat the process for that light. If there's another way to do it without going to live mode, do tell.

So in the interim, I took some of the lights that I use most often for arcades, bars, etc., and set their default light color to a dark red (even the darkest reds come out pinkish). For most of them, I did not play with the light's housing textures.

So now, rather than having to go through the rigamarole of putting a Sim on the lot I'm building just to flip light colors, I can grab one of these while in build mode and carry on. I may make other light colors in the future, like blue. We'll see.

Note: I set the purple ceiling lights to be REALLY BRIGHT and intended for use in rooms with essentially no other lighting and with black walls and ceilings.
Not shown are the ceiling lights. The red light collection also has a floor light for pools.

Catalog: Lighting (because of the way lighting properties are initially set on Sims objects, there is a different object in the catalog for each color).
Cost: 1 Simolean

Red lights:
Bunker Be Bright
Cutlass of Light
Laboratory Light Strip (Strangerville required)
Plank Perfection
Portal of Light
Subtle Saucer Light
The Harmonic
Terrestrial Saucers


Purple lights:
Bunker Be Bright
Cutlass of Light
Laboratory Light Strip (Strangerville required)
Portal of Light
Subtle Saucer Light