bright flowers get pollinated because the insect attract them because of the color of the flower
The flowers that are not brightly colored either have smell to attract the insects for pollination during night or these are pollinated by wind.
To attract birds and insects
bees
Some plants do not have flowers. Nearly all the plants you see around you are flowering plants: trees, bushes, vines, grasses and the "weeds". The flowers may not be big and showy, but they are there if you look for them. When flowering plants spread all over the world, about a hundred million years ago, they pushed aside the ferns and mosses and cone-bearing trees that had covered the planet for many millions of years. Of course, those plants are still here but they no longer have the planet to themselves as they did before the development of the super-successful flowering plants.
Wind-pollinated plants do not need colorful flowers as they are not pollinated by animals, insects or birds. Since wind-pollinated plants do not need colorful flowers, they might as well put their energy into making their pollen lighter, or more of it.
insect pollinated flowers are brightly coloured and sweet scented so that the plant can attract the insect towards itself.
To attract pollinators.
rose
Many colors have brightly-colored flowers; the purpose of this is to attract insects, which assist the plant in pollination.
Many colors have brightly-colored flowers; the purpose of this is to attract insects, which assist the plant in pollination.
to attract bugs to land on it. After landing on the flower pollen will stick to the bugs feet, so then when the bug lands on another flower, it will pollinate it. That is one way of how flowers reproduce sexually.
Petals are both wind pollinated and insect pollinated, not one or the other. Insect pollinated petals are large and brightly colored while wind pollinated petals are small and brown or green in color.