If those squares are finished at 8in, you should get away with a half yard for the blue and green squares, and maybe the lavender. That's also a generous amount for the strips. The brown sashing would be more, I'd think 1.25yds.
Squares would be cut 4.5" & 2.5" - strips 1.5 x 4.5 and sashing 2.5". Also I would consider cutting the sashing into 2.5 x 8.5" pieces, to make the block 10x10", just a thought.