If you are just going to use the blue as alternate blocks -
Are all the tractor blocks/units the same size? if so, just cut the blue the same size as the tractor squares.
There is no law that says that the blocks MUST be square - But all the same size and consistent sized rectangles would make it go together better.
It looks like there may not be much of that yellow 'border/sashing' around each tractor after it's sewn together -