Though some flowers are wind-pollinated, most are pollinated by creatures, including insects. You can tell the flowers that want to be pollinated by creatures by how showy they are. They are often large and beautiful, the better to be noticed by potential pollinators. They feature nectar to sweeten the attraction, and scent for those creatures with a good sense of smell. Some flowers have even developed to attract only certain kinds of pollinators, using color, markings and other devices to lure their preferred pollinators to them. Insects pollinate more than 65 percent of flowering plants.
You might wonder why snapdragons snap. The reason lies in their preference for the bumblebee as a pollinator. Only the weight of the bumblebee trips the opening of the flower. Once in, bumblebees can pollinate the flower.
Yucca flowers are pollinated by moths, specifically the yucca moth. Only this particular moth will fit the flower given its size and shape. The flower also serves as a shelter for the moth's eggs, which hatch and nourish themselves with yucca seeds.
Yucca flowers are light colored; light and white colored flowers are often pollinated by moths. The reason is that the white flowers are easier to see at night when moths are active.
Carrion flowers are so named because they smell like rotting flesh and mimic the color of it, too. Carrion flowers rely on insects that visit rotting flesh to pollinate them, especially flies, but also beetles.
Magnolia flowers are insect pollinated, but don't discriminate among them, having no particular preference for one bug over another. Magnolias are large and flat so bugs like beetles can crawl all over them, picking up or depositing pollen in the process. Beetles are thought to be the first pollinators. Magnolias, meanwhile, are ancient and primitive flowering trees.
Bees can't see red, so flowers that prefer bees as pollinators tend to be yellows, blues and violets, which bees can see very well, along with white. Often the flowers have colors that can't be seen by us since they fall in the ultraviolet range. The bees can see the colors though. The flowers also have petals that can serve as landing platforms for the bees. Violas have such platforms along with color markings that lead bees to where they can forage.