Colored boxes in the tag history

What is their meaning?

There seem to be all sorts of colors in various grades of light and dark, but I can't figure out what they mean or if they are just random.

They're explained here: http://danbooru.donmai.us/help/posts

I believe they were referring to the coloured boxen in the left-hand column on these pages:
http://danbooru.donmai.us/post/tag_history
http://danbooru.donmai.us/note/history

wanchan said:
I believe they were referring to the coloured boxen in the left-hand column on these pages:
http://danbooru.donmai.us/post/tag_history
http://danbooru.donmai.us/note/history

Oh those. Those are based on the post id. The idea was to let you easily notice posts that aren't part of a 1..2..3..4.. sequence that you get when people upload new stuff. If a color stood out, chances were someone updated an old post.