Florists love to sell “black” tulips, “black” roses, and “black” calla lilies. None of them are actually black. Plants make their colours from pigments called anthocyanins, carotenoids and chlorophyll - and none of those produce true black. The darkest a flower can manage is an extremely deep purple, red or maroon that just looks black to our eyes.
Evolution might have a reason. Black would absorb a huge amount of sunlight and overheat a delicate flower, especially in hot climates. Dark colours also reflect very little light, so they wouldn’t shine out to attract pollinators flying past.
Plus, bees don’t even see colour the same way we do. They see ultraviolet light and miss most reds. To a bee, a “black” tulip glows in deep ultraviolet patterns we can’t see at all - which is exactly the point.
