At my site this week, I wondered if the Double-6 dominoes could demonstrate a 7-coloring of a torus. Jason Woolever found a nice solution. With wrapped edges, all numbers are in groups. 0 0 0-3 3-3 3-2 | | 2 1 1-1 3 3-5 2 | | 2 2 2-1 1 1-5 2 | | 5 4 4-1 1 5 5-5 | | 5 5-4 4 6 6 0-0 | | 0 4-4 6 6-6 6-0 0-4 4-3 3-6 6-2 --Ed Pegg Jr