Then again, I could be off my rocker.
Yellow is for bees, blue for butterflies and red for hummingbirds. Yellow flowers bloom in spring because the bees are the first up come the season. Reds bloom after to lure the hummingbirds now home from Costa Rica. Blues bloom late in the season for the butterflies preparing to migrate.
Of course this is a very broad and general rule of thumb with a million exceptions. But the flora and their pollinating insects have learned through evolution the proper time that the flowers may be fertilized and the insects be fed.
Kinda neat, really.