We have developed a remote detection system consisting of commercially available retroreflective material coated with an analyte-specific colorimetric dye. Quantitative performance modeling predicts that, given the appropriate indicator dye, a system with a 10 cm optic and eye-safe illumination should be capable of detecting small droplets of contamination at kilometer ranges. We have synthesized new colorimetric dyes specific to organophosphate contamination and, with these dyes, demonstrated detection of 1um of liquid malathion at over 150 m with less than 20 mW of laser illumination.