I feel good about my color sense although of course we are all always improving.
An exercise I found quite helpful was to make a scrap quilt with a number of HST that were light/dark, done completely at random. I used some of my fabrics, some from old clothes and some from another quilter so the palette was larger than just what I typically use. I found myself analysing (but no changing!) each pair, looking at value, hue, color, warm/cool and observing what worked and what didn't. Even the pairs that didn't work well mostly played well in the final quilt.