How to customize message background and colors in the Messages app on iPhone?

My favorite color is green. I would like to have the option to display the text messages I send in a green background. I also like having a sort of background image/theme behind my messages. In a group message, it would be awesome to be able to set different message colors for people as opposed to looking at a letter or having to read a name in small print. When will Apple allow customization of the messages (text message and iMessage) being sent through the "Messages" app????

[Re-Titled by Moderator]