Rainstorm Sudoku

The variant is given such a name because of the many diagonal colour regions slanting in one direction, like heavy rainfall.

As in a standard Sudoku, the object of the puzzle is to fill in the whole 9x9 grid with numbers 1 through 9 so that each row, each column, and each of the nine 3x3 boxes must contain all the nine different numbers 1 through 9.

In addition, each diagonal colour region must be filled with the same number. Note that regions in the same colour on different parts of the grid do not necessarily contain the same number as each other.