column
            0  1  2  3
         0  .  B  .  .          Blue = (col & 3) == 1 && (row & 1) == 0
    row  1  .  .  .  R          Red  = (col & 3) == 3 && (row & 1) == 1
         2  .  B  .  .
         3  .  .  .  R          rest are Green