There are many ways to approach a scrappy quilt.
I tend to favor using contrast: darks vs lights.
I'll find or design a pattern and decide the position
of darks and lights within the block and roll with it.
(Perfect example is my avatar using a block I designed.)
String quilts are so much fun!
You can randomly grab a strip of fabric and go at it..
Or you can plan the position of color values and use that plan on each block and turn out some very attractive quilts.
...and you will have never really looked at the colors while you made it because the values have done all the work!