You can customize an iPhone by adding iPhone applications to the device. Apps allow you to add functionality to your iPhone. But apps approved by Apple don't allow you to customize the font, font size and font color on your iPhone. You can add apps that have not been approved by Apple if you jailbreak your iPhone. Numerous websites offer information on the jailbreak process. If you have jailbroken your phone, you can use the Cydia and WinterBoard apps created by Saurik to change text colors. Jailbreaking voids your warranty with Apple.
Tap the "Installer" icon on your iPhone. This opens the Installer interface. Tap the "Sources" icon at the bottom of the interface, then add http://apptapp.saurik.com/ as a source. Tap the "Install" icon at the bottom of the interface, tap to the "System" category, then tap to install "Cydia."
Tap the "Cydia" icon on your iPhone. This opens the Cydia interface. Tap the "Search" icon at the bottom of the Cydia interface. Type WinterBoard in the search box, then tap the "Search" button. Tap to download and install WinterBoard when it is displayed in the list of results.
Tap the "Sections" icon at the bottom of the Cydia interface. Locate "Themes (Springboard)" in the Sections page and tap to install any that you like. Tap to close Cydia.
Tap the "WinterBoard" icon. This opens the WinterBoard interface. Open the /private/var/stash/Themes.y9qoV5/Saurik/ folder and tap to edit the Info.plist file.
Type the color you want for your font, replacing the word "white" in this block of text with the new color:
<key>UndockedIconLabelStyle</key> <string>font-Arial: monospace; font-size: 12px; color: white</string> <key>DockedIconLabelStyle</key> <string>font-Arial: monospace; font-size: 12px; color: white</string>
Tap to save the edited file. The fonts on your iPhone will be changed to the color you selected for the theme.
Jailbreaking your phone may lead to its becoming permanently unusable. Jailbreaking is legal, but it voids your warranty with Apple.