no reason why you couldn't, that is how variations get born. The center of the red/black/white one above gives an example of neutrals.I saw one yesterday in oranges.
I don't press until the block is made but if my scraps were Really wrinkly, I probably would, just me. After a quilter's lifetime of precision piecing I am loving the improv of whack and sew.
I cleaned 3 layers of quilts off my working wall this morning, and while I have a brief space
I grabbed a pile of blues to see how I was coming along. This is just a fast placement, I have tons more blues, but I'm liking it!