By default, when Windows Mobile 6.5 is locked, you are presented with a greyscale Lock icon you need to slide to either edge of the screen to unlock your device.

If you like the looks of it, great, but if you find that a little boring you now have the opportunity to replace the graphic icon with a colored one. The files could even serve as a starting point for your future custom icons.

Download the zip file and copy the contents (four files) to your Windows folder on your device (make sure you overwrite the existing ones which you should back up too in case you want to revert). After a soft reset you’ll have the new icons.