It's a matter of understanding what the colours mean. Blue flashing items are usually related to a mesh problem. If you have blue flashing on your sim and you're not too fussed about tracking down the troubling item and can live with doing this every time it happens you can go to a mirror and change their appearance and exit out. Usually fixes the blue flashing (for facial stuff). Red flashing is usually related to a graphic error. Make sure your drivers are up to date.

If you've recently updated your drivers and this problem is happening since then, try rolling them back.