He said something like this
"They must be able to see colors, since the station was built in gray. And Marruk likes red, but not blue, which means they (the Karains) can distinguish colors. They know how to cry; when Tucker broke the phone, it said he heard Marruk crying. There was no mention of barking or howling; perhaps their language is barking, but only Tucker understands it, so to us it's like English. I don't even want to think about canine characteristics. I think I understand what you meant. There doesn't seem to be any involuntary tail wagging, but some factors influence it. Tucker saw Marruk's tail wagging under the blanket. Could it be because he was happy? They had just hugged."