I had several shirts that I embroidered with a black outline around an apple. These were done on the light colored shirts, when I switched to the dark colored I changed the outline to gray. These did not sew as nice. The gray did know go around the apple as cleanly as the black did and some red showed past the gray outside. The black is on spool #2 and the gray was on spool #14. I wouldn't think that different needles would sew differently. Any ideas on this??? Thanks, Michele