Tile Floor for the Painter's Room

I hand-tiled the floor for the 2nd floor painter's room from blue, green and white tiles purchased from the craft store. I used glass and tile adhesive glue onto pre-painted (on both sides) illustration board. After it was fully dry I used ceramic tile grout and then wiped it off after 20 minutes. What I learned: try to just grout inbetween the tiles, not on the tiles, as there is still residue on the tiles I couldn't remove.