[Agent Minivann]

It would only work with black, but you can use clothes dye. It's time consuming, and easy to make a mess, but you end up with tiles that are the same size as when they started, and they don't chip.

Get some black Rit Dye, a pot that you will never use for food again, and a slotted spoon (or similar) that you will never use for food again. Heat water to boiling in the pot, add dye, and then repeatedly dip the tiles in the hot dye solution. If they stay in too long they can warp from the heat. Do a bunch of brief dips and the water will turn black. I've done it and you can still see a little bit of blue on the bottom of the tiles, but otherwise they are almost identical to the shadow tiles from the D&D set.