Have run into this myself. Bought some glorious black fabric with gold outlined peacocks. For my dream project. Brought it home and laid it next to the focus fabric, and it looked as dull as could be. The black in the focus fabric was so much richer, darker, and "blacker". So now I take the fabric with me and it is amazing how many different shades are out there. And I agree, it is the same with many dark colors. Who knew there were so many reds??