By default, the iPhone 4 does not allow for theme customization. You are stuck with the typical colored chat bubbles unless you have a jailbroken iPhone. With a jailbroken phone you can customize the theme for the built-in SMS application. You will find a substantial amount of different SMS bubble themes in the Cydia app directory ready to install.
1. Turn on your iPhone and go to the home screen.
2. Tap the “Cydia” app and go to the “Search” section. Type in “SMS bubbles” in the search field and touch the “Search” button. A list of available SMS bubble modifications will come up.
3. Browse through the SMS bubble themes to see which one you like best. Some modification packages include multiple colored bubbles and backgrounds. Generally, on the theme listing page you will find an option for “Screenshots” or “Previews” that lets you see an image of what the theme looks like.
4. Go to the theme you want to use and tap the “Install” button near the top right corner. Tap “Confirm” and the installer automatically takes control of downloading the theme to your phone. You can install multiple themes and modifications without enabling them so you can have them accessible whenever you want to change your theme.
5. Tap the “Return to Cydia” button and then exit the application by pressing the “Home” button on your iPhone.
6. Tap the “Settings” app on the home screen and use your finger to scroll down the page. Stop scrolling when you see the “WinterBoard” option. Tap the button to enter the settings.
7. Tap “Select Themes” and then select SMS bubble theme you want to use. If you installed multiple SMS themes, you can only use one at a time, so check the one you prefer. Press the “WinterBoard” button near the top of the screen.
8. Tap the “Respring” button at the top and give the phone a few moments to restart. Move the lockscreen slider to the right and then tap the “Messages” app. Begin using the new theme you installed and enabled.