Moths feed at night, and are therefore most attracted to white or pale-colored flowers that are more visible at night. Moths also prefer flowers with a strong, sweet smell. Many insects also prefer flowers that have nectar guides on the flower petals. These guides lead the insect to the source of the nectar, and different flower have very distinctive nectar guides. Many of these guides can only be seen under an ultraviolet light, a wavelength of light that can be seen by insect.
Hummingbirds are the most common bird pollinators.
They choose large, tube-shaped flowers to match their long beaks. They choose flowers with lots of nectar because the hummingbirds needs lots of food energy to survive. The flower's anthers stick out above the petals so they are more likely to brush against the hummingbird and pick up pollen. Hummingbirds see red and yellow well, but have an underdeveloped sense of smell, so they often choose bright flowers with little fragrance. As you have read, many characteristics of flowering plants are directly related to the insects and birds that pollinate them.