Use list of hard coded colors instead of generating it.

This fixes 2 issues:
*Currently rainbow highlighting only works for the first 10 declarations
in Function and Other contexts. All other declarations get highlighted
with the default color.
*The current interpolation algorithm is very poor, it can generate only
about 10 different colors, all other look alike.

So this patch adds ~35 distinguishable colors, which should
be more than enough for most cases.

REVIEW: 123809