15 teams in the tournament.
3 teams play in each game.
7 games are played by each team.
35 games are played in the whole tournament.
Each team plays every other team once.

Game
A1B1C1D1E1F1G1H1I1J1K1L1M1N1O1P1Q1R1S1T1U1V1W1X1Y1Z1A2B2C2D2E2F2G2H2I2
Team1R Y GR Y G R
2GR Y R Y G R
3 GR Y G R Y R
4 GR Y G R Y R
5Y GR G R Y R
6 Y GR G R Y G
7 Y GR G R Y G
8 Y GR G R Y G
9 Y GR Y G R G
10 Y GR Y G R G
11 Y GR Y G R Y
12 Y GR Y G R Y
13 Y GR Y G R Y
14 Y GR Y G R Y
15 Y GR Y G R Y

The above grid contains back-to-backs. Creation of a grid with no back to backs is simple, and is left as an exercise to the reader. :-)

13 team Tournament Grids 16 team