Obviously, unless the extraterrestrials know a lot about our solar system and are deliberately targeting us with a broadcast, there's a much greater chance that we'll be in someone's radio beam than in an optical one. Some optical observations have been made, and Stuart Kingsley in Ohio is running an optical SETI experiment now. But for the moment at least, most scientists are betting on radio. If you walk into your local electronics store, you will be greeted by a wall full of television screens showing the same vividly colored images. When you begin to inspect the images more closely, you will notice subtle differences in shadings and skin tones from one set to another.
Astronomers putting together color images face the same problem.
Individual images taken through different filters, frequently at wavelengths the human eye cannot detect, are combined in a standard blue, green and red format. Sometimes an attempt is made to approach the natural colors of objects. Often, contrast is deliberately enhanced to bring out details. This way of looking at data can be a powerful way of seeing, at a glance, phenomena that would be difficult to describe in other ways. But for this kind of work, the most powerful tool is a spectrograph that accurately measures the variations in brightness with wavelength on a scale far more detailed than can be perceived by the eye.