--- EDIT ---
Now with SVGs
These Icons replace the standard Icons from the CPU Frequency Applet for the Gnome Panel. The colors fit perfectly to the new monochrome panel icons in Ubuntu 10.04 Lucid Lynx.
To install do the following:
- Extract the archive to a temporary folder (e.g.: Desktop)
- Copy the extracted files to the clipboard
- Open a File Manager with root permissions (e.g.: sudo nautilus)
- Navigate to the folder "/usr/share/pixmaps/cpufreq-applet"
- Paste the copied files and overwrite the old ones (Backup the files if you want the old ones back).
- Log off an log in again or open a terminal and type "sudo gtk-update-icon-cache -f /usr/share/icons/hicolor" and remove the applet from the panel and add it again.