Q My Finder icon, as shown in the Dock, has developed what appears to be grey hair around its upper corners. I know my iMac is over four years old now, but is this really Apple reminding me to upgrade it?

A I cannot ever recall seeing this odd effect, and do not know of any OS X or third party product that is capable of doing it. It certainly does not show on other older Macs.

Sometimes a little screen redraw ‘dirt’ can get deposited on the Desktop or other interface components, but this is never persistent, and disappears once that area has been properly redrawn. It should certainly not persist after a restart, for instance.

The only situation in which this type of change is used as a signal to users is on Windows networks, where it can indicate that there are too many users. Whilst this does not seem likely for a Mac, if you are connected to a server-based network that could be responsible.

The other faint possibility is that this has been set by a third-party customisation tool. If you cannot recall using a product that might do that, restart with the Shift key held down to disable all such extensions in Safe mode, and see whether it disappears. This should also clear the Dock’s icon cache which could have acquired a corrupted copy of the Finder icon.

Failing that you could look for some software Grecian 2000!

Comments In all the many years and thousands of questions, this is the most bizarre that I have come across, and remains unexplained. Yes, the grey hair suddenly disappeared, but I have never found out what caused it. Does anyone else know?

Updated from the original, which was first published in MacUser volume 27 issue 24, 2011.