How does mimicry in sounds help animals survive?

The predator eventually learns to associate certain bright colours with danger, so they avoid eating animals with those colours, poisonous and non poisonous alike.

What happens is a non poisonous species that look similar to poisonous ones are confused for being poisonous by the predators if they're colourful. The ones that look the most similar aren't eaten, and they're the ones who survive and pass on their genes, causing the following generations to look more and more like the poisonous ones.

It's sort of "accidental" natural selection.