My first thought was to connect all four blocks with inchies in the challenge block colors.
My first impulse was to turn them on point
and add these fabrics all around. My blocks are not very exciting and I wanted to jazz them up.
I think my intuition that they were not visually interesting was on the mark. By adding more strips all around of the fabric already used in the initial block, I think they are considerably better. To tie the blocks together I made one change which was to substitute a solid blue strip for the challenge color strip. But the blue strip is right next to the challenge color in the original block.
So, for the time being, this is what it looks like: