Hi Monti2,
In my experience, the flashing pink/red light is nothing to be concerned about... so long as it's still charging your device that is! I've found two reasons that happens: 1, my phone is already fully charged. 2, I've got the USB power cord plugged into a cheap charging cube, rather than the one that came with either the charger or my phone. Either way, I believe it to signify that the charger is not charging at maximum capacity, 1 to keep from frying an already charged battery, 2 because of being powered by an inferior power source.
Hope this helps!