Here's the way to check for that 1/4" seam:
http://www.quiltingboard.com/tutoria...ce-t89997.html
Having said that, if the diagonal green and blue strips are supposed to meet the edges of the borders around the blocks the strips
cannot all be cut the same width. It's mathematically impossible for them to meet perfectly in the corners. Double check the pattern and see if the diagonals are supposed to be cut wider or the borders narrower, the strips should be different widths.
In the quilter's cache version, they cut the strips 1.5" for the sashings and 2" for the diagonals:
http://www.quilterscache.com/G/GardenMazeBlock.html