If a comment is net negative, it is shown in a hard to read color, the more harder to read the more negative it is. I don't know how many different levels there are, but here are the colors I've seen:

   #e6e6e6
   #9c9c9c
   #737373
   #bebebe
   #aeaeae
   #888888
   #cecece
   #dddddd
   #5a5a5a

At the time I asked why he was getting down voted, it was at least a net of two down votes, because I up voted and that did not restore the comment to the normal color.