Interaction between \hdotsfor and colortbl: Bug/Feature?

Since \hdotsfor is only really designed for the AMS alignments, and colortbl colouring doesn't really work for them, I think the simplest is to add

\makeatletter

\def\hdots@for#1#2{\multicolumn{#2}c%
  {\m@th\[email protected]\mkern-#1\dotsspace@
   \xleaders\hbox{$\m@th\mkern#1\dotsspace@.\mkern#1\dotsspace@$}%
           \hskip\z@\@plus 1filll
   \mkern-#1\dotsspace@}%
   }
\makeatother

to your preamble after loading amsmath that makes these stretch with filll rather than fill glue which means that in the battle of elasticity with the colortbl the dots win.

If you wanted a version of \hdotfill that worked even if there was a colortbl panel behind it then it would require a bit more work.