Silicone holds those tanks extremely well, and the rims are mostly cosmetic, unless you are using narrow tall tanks and fill them with water. Without water, if you just house your hamsters in one, the rims make no difference in the structural integrity of the tanks.
Problem with the rims is that they are held by silicone. As biscotti described, you will need a razor blade to separate the rims from the glass, and you can definitely crack the glass in the process, when trying to wiggle the rims off. I'd done some research on it in the past, as I own large aquariums, but I decided it wasn't worth the trouble. My tanks are painted instead (regular good quality drywall paint):
Red
Beige
I matched mine to my rooms, and I love the looks. Use a small paint roller. I'm not sure where you live, but if in the U.S., Home Depot sells Behr Ultra paint at $3 per sample can in any color you choose, so it's a good way to paint aquarium trim very cheaply. Since it's not oil-based paint, it will chip and scratch if you are not careful about scuffing it, but I almost never need to touch mine up.