Definitely part of the reason I'm doing a gemstone- I think you get really pretty colors for less money than if you bought the "real" version of the stone- you can get really gorgeous green tourmaline for the cost of a low-quality emerald.
On a general jewelry note, I usually don't like blue topaz (I like the icier blue color of aquamarine) but I found out there's different types of blue topaz- right now I'm drooling over a necklace they sell at Costco (!) with a London Blue Topaz pendant. It's sort of a dark, blue-green color. I can't find a picture of it, but here's a similar one:
My parents have cashmere sapphires in their rings....a dark dark aquamarine colour. The stones are pretty but I'm not big on their settings.
But then I tend to be the opposite of you and I like darker coloured stones better than lighter.
Watermelon tourmaline would be pretty in a ring too!