I found online instructions for how to colour grout. You just mix some acrylic paint into the water that's used to mix the grout and then add that to the powder grout. I was thinking about doing this for the tiles I had already made so I decided to do a test where I would grout one plain and th other using the coloured mixture. When the white one was set I would then paste a small layer of the green grout onto the white one and see if that would work. It did work but I decided I didn't like the colours for the tiles, so im just going to leave them white.
