I vote for the blue also..

the blue blends & sets the blocks. yellow floats them.
try a sashing of blue,yellow, blue.about 1" @ finished. where they meet for the cornerstones, make a reverse 9-patch.
would be very striking. pretty blocks.

The blue looks blue/gray to me... my sons would love it. The yellow would be for a girl or woman. It looks lovely, either way.

I love #3. It just seems more cheery.

blue gets my vote

I like the blue. The yellow pops on that blue.

blue

blue

Blue for me.

Blue