Yahoo! Messenger allows you to change the default font and color that will appear in instant messages. Here's how:

1. In the main Messenger window, click on the "Login" menu.
2. Choose "Preferences."
3. Click the "Appearance" tab.
4. Click "Fonts and Colors" to set the default.
5. Click "OK" at the bottom of the "Preferences" window, and presto! -- changes made.