A square wall is laid with small square ceramic tiles of red and green colors. Counting from the outside to the inside, the outermost layer is laid with red tiles, the second layer is laid with green tiles, the third layer is laid with red tiles, and the fourth layer is laid with green tiles, etc. A total of $400$ blocks of ceramic tiles are used. Find which color of tiles are used more on this wall, and the difference between the numbers of the two colors of tiles on this wall. 
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