We've been transmitting radio waves into outer space for decades. So, it shouldn't come as a surprise if we aroused attention. If we are already being watched, in what lightwaves would the visitors view us? What would they think of us? Would we be able to see them?

If they are advanced enough to reach Earth, it is highly likely that they would be able to cloak themselves to make themselves invisible to us, until or if they decided to make contact.

Humans though have limited vision, only being able to discern their environment in values of Red, Green Blue. Just a small part of the known color spectrum. 

Is it time for us to expand our vision?