At least you did the entire quilt with the same bobbin. I changed projects, changed bobbins, then forgot to switch back when I returned to quilting. It was a baby quilt, not a wall hanging. Lots of seam ripper time :(

Color the back thread only if it will make you happier. We won't tell and we all have blunders anyway.

Make up your own rules as you go along. You are the police. Unless you are giving it to your MIL!!!