I have had this question often enough to answer it publicly. How do I choose fabrics for a scrap quilt? After the fabrics are selected, do I consciously choose where each will go in the quilt? Why do the scrap quilts I make look so coordinated?
There are so many aspects to making a scrap quilt. Here is the usual progression for me...
I am piecing a quilt top. I have my next quilt to make selected (in my mind, at least). I start cutting some units for the NEXT quilt while I'm finishing up the one being sewn. I cut up what's left over from the first quilt and try to use up my scraps (which are in plastic shoe boxes...a couple colors in each box). I use "new" quilt units as leaders/enders as I finish sewing the one in progress. By the time I have the in progress one finished, the second one is well under way. Usually at that time, I have quite a few blocks finished, but not all the pieces cut for the (second) quilt. It is at that point that I stop cutting any ole scraps on my cutting table and actually see if I need more or less or a color to have a good balance. The same is true for value...do I have enough lights to make the top sparkle? Too many? I will purposely pull out the colors or values that are missing to make the top pleasant.
In this top I used greens in the 4-patches in the center of each block, but did not use greens in the outside "twin peaks" units that touched the green triangles on the outside. I didn't want the greens to blend together and lose the design of the quilt.
When it came to laying out the finished blocks, I did not put any of the creams next to an identical one (the triangles around the 4-patches are all one cream in each block). I also turned the blocks so that no identical green outer triangles were next to each other.
I am blessed to use MOSTLY Thimbleberries. They all kind of go together. When I was nearly finished with the 4-patches, I found a little baggie of sample fabrics that were 2" squares (sent from a warehouse as samples of a new line). I just made the rest of the 4-patches from that bag since they were already the right size. To look at the quilt, you'd never know which ones were the "new" prints.
One rule of thumb is that if a fabric really sticks out when you look at the top, you should put it in several other places (spread out) in the top. I posted about this a long time ago here. I tried to find the post, but I can't. Sorry!