(Click on the photo to enlarge it.)
The Rainbow Eucalyptus tree has this beautifully colored bark. Patches of outer bark are shed annually at different times, showing the bright-green inner bark. This then darkens and matures to give blue, purple, orange and then maroon tones.
The photo was taken with a Canon EOS 40D, EF24-105mm f/4L lens, 1/60 sec at f/9.5, ISO 640 on SanDisk Extreme IV Digital Film.