well, most ppl say you need at least 30x... but since you can actually see the trichs with the naked eye, if you have real sharp eyes you might make out the colours with one of those 10x thingies...
i have a 30x and it works perfectly for me. itll be a little harder to make out details with a 10x but youll figure it out. if not, get a 30x, theyre 6 bucks.
30x is usually the minimum as even 30x gets hard to see. 10x just won't work to correctly see the shades of the trichomes.
Ive got 20/20 but I don't think thats applies here lol. So I got the 10x at a science store, it was the biggest they had, unless I got a microscope - where the price jumped dramatically Ive heard Radio Shack has them, is that where you got yours?
I just bought the one from radio shack. Works very well, but don't forget AAA batteries, there is a plastic piece than throws a shadow and the lights does a good job making up for it.
You can find 30x loupes online easily for under $7 shipped. That really is the best way to do it, once you get the hang of using them you will wonder why anyone uses anything different.