In my opinion, it doesn't matter much. I make sure my tension is correct, and I use Bottom Line (60 wt) pretty much exclusively. The thread is rarely visible on the top side of the quilt. The only time I make sure I use a certain color is if I'm working with light fabric, I don't use black or dark thread because it can show through the fabric.
Last edited by Peckish; 10-17-2021 at 08:35 PM.