Its evolved as a defence mechanism, by why the bright colour? Bright colours such as red in nature are there to stand out amongst the green, sometimes to signify fruit, other times to warn! In the case of ladybirds, they are red because its a warning to potential predators that they are poisonous and to stay away. However, that’s a bluff as ladybirds are not poisonous, which can happen at times. There’s a great example of two types of snake. Both look nearly identical, really colourful but slightly differently oriented stripes. One is lethal, the other completely harmless. Its natures way of playing poker, calling a bluff!