electromagnetic spectrum mystery

in th game of clue, mrs. white is killed in the conservatory. you have a device in each room to help you find the murder, a spectrometer that emits the entire visible spectrum (from 400-750nm) to indicate who is in that room. for example, if someone is wearing yellow is in the room, light at 580nm is reflected. the suspects are Col. Mustard (yellow), Pro. Plum (violet), Ms. Peacock (blue), Mr. green, and Ms. Scarlet (red). at the time of the murder, the spectrometer in the study recorded a reflection of 520nm, those in the lounge and library recorded reflections of lower frequencies, and the ones in the dining room recorded a reflection at the shortest possible wavelength. who was in the conservatory and killed mrs. white? explain your reaoning by indicating which room all of the suspectsts are located.