The Windmill Square is alot of fun.  It is an easy pattern to sew.  I have chosen soft colors with a slight contrast.  There are many options you could do with this block.  You could have a greater contrast with the t-shaped part of the block.  Or keep that lighter and the greater contrast on the pinwheel, making the pinwheel pop.  

I was making a baby quilt so I wanted a soft look.  Take a look at what happens when you put the blocks together.  

With different values of color, you could have the pinwheel pop or the other square pop.  Have fun with it.  You could also stand the block on the diagonal. 
Enjoy!