Damn, this looks cool!

Can't wait for the comments (Will they have their own new column a well? Of course they will, right?)
Haven't tried it yet (but will soon), but reading the changelog you seem to "focus" on Color : column "Color", search/sort by color, etc -- Shouldn't that be "tag" instead (as the name of the feature implies) ?
That would sound much better to me, a column "Tag" which we can use to sort/search files, and each tag could optionally have a color assigned. I say optionally because I would also like to have the ability to "group" files by assigning them the same tag, and yet have no colors set, just the usual color filters stuff. (i.e. the tag only be used to sort/search)
I would think it might be even better that way, so the tag.dat structure would read more like:
With each tag having its index, name, and only optionally a set of colors. (Of course, maybe that's already your plan...)