I cannot believe I didn't know of their existence!
"The trees get their name from the striking colours observed on their trunks and limbs. Although it may look like someone took a paintbrush to them, these colours are entirely natural. Unlike most trees, the rainbow eucalyptus does not have a thick, cork-like layer of bark on its trunk. The bark is smooth and as it grows it 'exfoliates' layers of spent tissue. This exfoliation technique occurs at different stages and in different zones of the tree.
Once a layer is shed, a new fresh green bark is exposed. As this new bark ages, we can see the tissue change colour to dark green followed by a bluish colour, then to purple and pink-orange and then finally to a brown pigment right before exfoliation occurs.
As this process occurs at different rates and in sporadic areas of the tree, the colours are constantly changing, resulting in unique patterns; a living work of art."