  We suggest a new color distance based on two observations. First, perceptual
color differences were designed to be used to compare very similar colors. They
do not capture human perception for medium and large color differences well.
Thresholding was proposed to solve the problem for large color differences,
i.e. two totally different colors are always the same distance apart. We show
that thresholding alone cannot improve medium color differences. We suggest to
alleviate this problem using basic color terms. Second, when a color distance
is used for edge detection, many small distances around the just noticeable
difference may account for false edges. We suggest to reduce the effect of
small distances.
