NEW YORK (AP) — Some flowers have found a nifty way to get the blues.

They create a blue halo, apparently to attract the bees they need for pollination, scientists reported Wednesday. Bees are drawn to the color blue, but it's hard for flowers to make that color in their petals.

Instead, some flowers use a trick of physics. They produce a blue halo when sunlight strikes a series of tiny ridges in their thin waxy surfaces. The ridges alter how the light bounces back, which affects the color that one sees.

The halos appear over pigmented areas of a flower, and people can see them over darkly col...