Of course it depends on the wavelength, but single band images look a lot like any grayscale image. It's typically only when different single-band images are compared side by side that the differences really jump out. Which is, of course, why they bother with multiple bands. I worked on the lunar reconnaissance orbiter camera, and was involved with image processing and calibration for the wide angle camera, which is multiband (5 bands in visible, 2 in UV).