I am a longarmer and it is very hard for the dots to disappear without changing the tension, The LA tension is a pain to keep adjusting. I did it once and never again.
I don't change the thread colors so the bobbin is different,all the colors are the same top and bottom.
I do quilts for cust who entered them in shows and they win ribbons,so the thread being the same color as top and bottom is okay.