Which Color Block Completes the Grid?

Official explanation

Solution Think of each tile as a 3×3 grid of equal cells. Across the first two rows of tiles, the totals for red, green, and blue are 7, 6, 5 and 5, 7, 6. The totals rotate, so the bottom row should have 6 red, 5 green, and 7 blue cells. Its two visible tiles already contribute four cells of each color. The missing tile therefore needs 2 red, 1 green, and 3 blue cells. Both A and C match those counts. To tell them apart, look at the full-length stripe in each tile. Each column of the large grid has one vertical stripe and two horizontal stripes. The rightmost column already has a vertical stripe in its middle tile, so the missing tile needs a horizontal stripe. A meets both conditions.