Before going any further, be sure to measure and square up your nine patches.  If they are all within 1/8", you are good to go.  If not, pick the smallest one and square up the remainder of the blocks to that one. 

This is where the third color can come in; it is optional.  If you would like to make a more traditional Irish Chain, keep the same background (in this case it would be the solid light pink).  I have chosen to bring in my third print, Yuwa pink gingham.