for the 2 color corner triangles i would sew a 4 patch together.
lights on opposite corners and darks on the other corners and then cut the block in half on the diagonal thru the dark squares.
that will leave you with 2 large triangles having an entire light color square with 2 dark triangles attached to it.
you would have to make 2 of these 4 square units to cut in half yielding four 2 color corner triangles.
does that make sense to you?