Why dont we see colours in an electron microscope?

Because what's being visualized in EM are not photons which we perceive as light and color. Instead of photons being shined on the sample, electrons are fired at it. What is visualized are electron densities. Matter is electron dense and will deflect electrons being fired at it, preventing those electrons from reaching a device that receives and measures electrons. Thus, we're really visualizing a shadow of sorts. INTERESTING