The response of western flower thrips,Frankliniella occidentalis(Pergande), to color was determined by varying the hue, intensity, and saturation of 84 sticky traps in cucumber greenhouses. Male and female thrips alighted preferentially on traps of bright blue, violet, yellow, and white, whereas green, orange, and UV-reflecting white hues were not attractive. Reducing the reflectance intensity of the attractive hues resulted in a linear reduction in the number of thrips trapped, but reducing the reflectance intensity of the nonattractive colors had no effect. Sufficiently desaturating the attractive hues with white or UV-reflecting white paint resulted in a decreased response, which was attributed to interactions between key wavelengths reflected at 350 nm (UV), 440 nm (blue), and 550 nm (yellow). The addition of yellow wavelengths alone or in combination with UV to a blue hue had negative effects, and the addition of blue wavelengths alone or in combination with UV to a yellow hue also had negative effects. From these data. regression models were developed to predict the response ofF. occidentalisto traps with dominant wavelengths between 400–650 nm, with or without UV reflectance.