Flowers of plants that are pollinated by animals such as birds or insects are usually colorful. Colours sometimes helped by coloured guiding marks attract animals. Also, flowers are often shaped to provide a landing platform for animals, especially insects or have scent to attract them. Flowers adapted to birds’ pollination are often long-shaped with lots of nectar.
When it comes to wind-pollinated (or water) plants, it is important for them to produce a huge amounts of pollen, to have small petals or no petals at all (like grass). Also, the stigmas of receiving flowers have to be sticky.