What's the purpose of the multi-colored tab?

When you see color blocks, such as on the multi-colored tab and on the individual portfolio notes, you can change the background color of the screen to one of the colors shown.

Most browsers let you do it by simply running your cursor over the color block. Some browsers make you click on the color block.

It's a perfectly useless feature that has very little to do with anything except that it's kinda fun.