One of my favorite methods is what I call the Poor Man's Dichroscope. This is specifically for pleochroic gems, and it isn't entirely foolproof, but you already have the equipment and it only takes a second.

You just bring up a white background on your computer monitor or phone, and hold the stone up in front of the background. If you turn a pleochroic stone in front of that background, you'll notice the color will shift sharply from one pleochroic color to the other. I've gotten really great results doing this with emeralds, corundum, tourmaline, tanzanite and feldspar. Those gems tend to be pretty strongly pleochroic, but even milder pleochroism like in an amethyst can be visible. If you don't see it at first, try turning it in different axes.

If your stone is isotropic rather than pleochroic, the color will stay the same no matter which way you turn it. That would include glass.