Go to Options >Security Options >General Settings. Scroll down to "Message Colors." Change them to "None."

It's a feature added to easily differentiate between different email accounts or between emails and pins. In OS 4.5 it's been changed to a colored outline around the text box.

There's no need to revert back to 4.1. I'd recommend sticking with 4.2 until someone releases 4.5 for the 8703.