We have all three of the colors you mentioned - red, orange, and yellow. Look at the beam spreads here. The orange is good, but I'm not sure what "niche" it fills (the son who uses that one likes it, FWTH). The red and the yellow have different uses IMHO. The yellow is...interesting. I use the red - and it is a rather bright red; a bit too bright if you're not careful, although it is a pupil dialation/contraction effect, rather than a night vision adverse effect (less time to recover). These are are fundamentally short range devices for most uses and I find the wider beam spread on the red to be more useful for general tasks than the orange or yellow. I like the yellow well enough, though, to seriously consider it as a replacement for white in my FAK for longer trips - and it's a tidy one for reading in a shelter after dark.

Since they are usually sold at a considerable discount if one purchases two at a time, why not purchase a red and a yellow or a red and an orange?

My 2¢ worth...

Tom