Unfortunately, achieving the perfect tension of not seeing bobbin on the top or top on the bottom is one of those grand master ninja quilter things . that being said, there is a somewhat unconventional method of , faking it ! In your case it would be easy since it is the red showing on the black, if it were me, and it REALLY bothered me, I would use a fine tip black permanent marker and ever so carefully, cover the red that peeks through in the most noticeable spots.