Choose chat bubble colours in Messages.app, you can select colours for SMS bubbles, iMessage bubbles and other person bubbles, as well as the Messages.app tint colour. In addition are options to hide message bubble tails, show/hide contact pictures in the conversation list view and enable wide message bubbles.
Colors for the chat bubbles include Green, Dark Blue, Light Blue, Purple, Red, Teal, Dark Grey, Light Grey, Black, Yellow, Orange and Pink. That tweak also works with BiteSMS, and supports ARM64 devices (iOS 7 only however).
You can configure Message Customiser through the Settings app once you install it via Cydia. You can find it on the ModMyi Repo for Free.