There are so many good, artistic, directions you can go with choosing colors for a quilt. Here is one simple way to use color that appears to contrast with blue but actually complement it in a very eye-appealing way.
So, Let's think about this.
Blue is a true/"primary"/pure color on the color wheel. It's companions are red and yellow which are also pure.
If you choose to go "pure", perhaps you could make your alternating blocks red and the setting triangles for the on-point edges in yellow (or vice versus). Prints, blenders, etc. can still be used in this way.
If you wanted to go triadic (3 colors in your quilt) then you could choose to use the variations of blue -- the color to the left of blue on the color wheel and the color to the right of blue on the wheel -- in this case blue-green and blue-violet.
Or you could choose to use three side-by-side colors across from blue on the color wheel....in this case yellow/yellow-orange/orange. You have seen blue and yellow quilts; they are a popular favorite because of this artistic combination using the color wheel.
If you choose blue and yellow combinations, small pops of orange/orange-red will really brighten your quilt and add to its eye appeal.
The blue and green combinations mentioned by others are also good, and will be improved by bits of rust/reddish-brown or tan, maybe in the print or as the middle of the 9 patches.
It'll be interesting to see what you come up with.
Jan in VA