What parts of flowers attract insect?

The part of the plant that actually attracts insects is the colorful petals, once they've landed on it, the pollen attached to the stamens makes them stay and gather it. Certain insects can actually sniff out the actual pollen, but its the flower's color that initially draws them in.

The pollen, which is produced by the stamen, or male part of the plant.
The stigma attracts all the insects because when stinking fiys fiy around the plant is because of the pollen!