There are several ways to color epoxy. Of course, there is first of all the clear epoxy where no dyes have been added. You can also color epoxy with:
Metallic pigment powder
This powder provides a metallic color (2 shades of the same color, with a sparkle in it). This variant is not transparent.
Transparent color pigment
This liquid gives a transparent color to the epoxy, which you can see through. If you added more liquid, the color will become darker and less transparent.
Solid color pigment
This dye gives the epoxy a solid, opaque color. Usually black or white is chosen for this variant of colors.
Glow in the dark pigment
A very cool option is to color the epoxy with glow in the dark powder. This is often combined with a metallic color in the bottom layer and a transparent layer in the same color, usually green or blue, on top.
Casting objects in the epoxy is also very cool to see. An example is the river table that I made with the cast-in stones, shells and a glass fish so that the river of the table really looks like a river!