I don't know the proper term is for the label that appears when the mouse cursor is left over one of the launcher items. It's shaped like a gardener's plant label, with the name of the application written on it, and is usually dark grey with a white edge and with transparent triangles at the sharp end.
After several weeks of using Unity, I've noticed that the transparent triangles have become red, and affect most, but not all, of the launcher icons. As I type this, all the launcher items except those for "Update Manager" and "Rhythmbox" are affected.
This doesn't happen every time I boot up my system, so I suspect it is a bug not a feature.
PS The last time this happened, I found that clicking on the Dash icon didn't open up the dash as usual, just a close/minimise/maximise bar at the top left-hand corner of the screen. A reboot has fixed it (for the moment). I think it's possible that this problem is linked with the software updater. I'll keep an eye open!