Many insects and amphibians and even some mammals (skunk, for example) advertise their unpalatability – or dangerousness – with easily recognisable colour patterns.
The phenomenon is far less well documented among plants. One possible example is the lancewood tree of New Zealand, the saplings of which are armed with spines on their leaves.
The leaves of the spiniest plants are also adorned with patterns of white spots, thought to have evolved to advertise their formidable defences to giant moa, now- extinct flightless birds.
There is a theory that the brightest- coloured autumn leaves are produced by the healthiest trees with the best chemical defences. Redder leaves may deter herbivorous insects such as aphids from from selecting these trees as winter hosts.
Main image © Kahuroa, Public domain, via Wikimedia Commons