Can you change the colour of the LED light on the Samsung Galaxy S3? On the top of the phone there's a light that flashes blue when you get a text. Is there an app or setting that can change this so the colour is different for some senders who text you?
There is powerful and full-customizable GO SMS PRO which lets you set any LED color for sms incoming notifications based on sender. Also, it is a mighty alternative for stock sms app and has many useful functions and customizations.

After you installed it, run and tap menu, then Settings, and go to Advanced -> Individual Settings and add any contact to set individual notification (including LED options) for it.