When i was much younger, in a class somewhere, i saw pictures of flowers
taken with somekind of UV filter.  Different species of flowers had
different patterns when viewed with UV.  So a human sees solid yellow
flowers, but bees see patterned yellow flowers. The thought at the time
was that, flowering plants used this as a strategy to keep a bee
interested in its species, creating a greater chance that its individual
pollen will rub off on a flower of the same species.  Supposedly in a
garden full of different cucurbits, one can see an individual bee
visiting all the cucumber blossoms then all the squash etc.