Found the uses for Blue and Green. Green is good for mid game when you can instantly bring it to at least level 4~6 depending on the map (or start game only on a long winding path that gives you double starting cash); only works on maps with low enemy count per wave to counter it's randomness + should still be replaced with Yellow when possible though. Blue is good where *many* enemies cluster together, usually closer to the entrances. Blue can even out-perform Yellow's dollar-to-DPS ratio when it consistently strikes 10 enemies per shot using optimal placement; 2500*10=25000 damage per shot. You'll only want to swap them out for Yellows once literally *all* other turret spaces are taken when they're placed optimally; they'll last you a good long while into the post-game even if they do get replaced eventually.
@lange: Alright, just thought I'd check if anyone else found any use for those towers that I didn't find. Yeah, there's only a select few maps where you'd ever need a level 5 red; most properly balanced maps it's indeed as you suggest. I usually pretty much only play custom maps that look properly challenging rather than looking like another one of those high-score machine maps or straight-up troll maps. While I didn't intend for my most recent upload ("Indisputable Hardest Map Ever") to be a troll map I can't seem to get past the first Red Diamonds without losing a metric ton of lives, so I'm starting to wonder if I should remove it....
Okay, starting gold needs to be a manual input instead of a checkbox. I just uploaded a map that feels like it should be possible even though it's tougher than nails and then some. After some further play testing though, it locks me into laser arrays and then utterly destroys me on the very first red diamonds wave. There's literally no way that I can find to break out of that cycle, and losing out on any gold means an impossible game on that map ;/ If it really must be checkboxes, then there should be a checkbox for causing towers to sell for their full worth on the map.
Red = early waves, Yellow = easy kills from a high range, Magenta = damage multiplier, Cyan = keep enemies in main damage zone longer. Anyone know what Blue and Green are for? Those are the only two that I can't figure out the uses for.
@Mydiz
Technically up to 9... though for most maps the highest level you'll want a laser array to be is level 5 (5 lasers) before selling it prior to a Red Diamond wave to purchase and or strengthen other towers. At least from my experience; your strategies and therefore mileage may vary.
 "Chromatic Tower Defense"){kind=icon}