All the flag in the world are made of different colors. The number of flags with one color is 1, 2 colors is 43 flags, 3 colors is 76 flags and so on. You can check out the different colors of different flags in the world at this site http://www.crwflags.com/fotw/flags/xf-csts.html. There are 192 flags in the world.
Blue and white are common but i dont think any single color is shared by every flag. The colors of the Olympic Rings - are red, green, blue, yellow/gold, and black. Every flag in the world has one or more of these colors.