random swap the block (block will have color)

![alt text][1] [1]: /storage/temp/108310-block.png I have 5 blocks in my 2d game and a player(blue color) i want random(only four color) color in my 5 blocks at one time when spawned (color must be diffrent) when blocks come to top to downi want my player (blue color) to go from blue block(i mean same color ) if my player touch diffrent block game over can anyone tell me how do i code ? i mean steps i am newbie thnx for answer