It does look a little bit nicer if the shades are grouped together. I try to find the smallest pieces to start with.
Sort your fabric scraps by color
I try to find pieces that are similar in size. Then line them up, right sides to right sides with a shared edge.
Line your crumbs up
The idea is to add to your original crumb and just keep adding to it and getting bigger and bigger, working to create one bigger square shape.
Chain piece the crumbs together
When I feel like I have enough pieces together, I cut the thread.
Each time I add a crumb to another piece, I take them to my wool pressing mat and press the seams with my iron to one side.