Your problem is in assuming that there is a finite number of universes created. Instead Think in terms of an infinite number of universes created, of which 2/3 of them are red, and 1/3 of them are blue.

(E.g. Imagine all the universes created map to the range 0 to 1, and the first 2/3's come up red, and the last blue (or reverse that, or shuffle it up). The mapping onto 0 to 1 is merely for visualization purposes, and is thus arbitrary.)