Pollinators such as bees, birds and insects are nothing but vectors 'agents' that aid in transferring the pollen from one place to another. Floral parts can be showy, fragrant and abundant. But when it comes to biotic vectors such as bees, birds, butterflies and hundreds of insects, what sells most is the POLLEN!
"There are several ways to attract a vector. When the vector is an animal, the flower will use olfactory or visual signs. An example of a visual sign would be a color pattern that attracts the animal's attention to the pollen. This is also known as a bulls eye pattern. The color of the flower and its center affect the type of vector that it attracts. Different animals see some colors better than others. Butterflies, for example, are attracted to the red/yellow color pattern."(https://faculty.atu.edu/cbrucker/Engl2053/Samples/bjb08.htm)
Plants also depend on abiotic vectors such as wind, water etc. But for biotic vectors they have to work hard. The evolutionary patters on flowers to attract biotic vectors is fascinating to say the least. Check out the slideshow below for some examples.