Ears are part of the hairstyle. Some have colour variations built into the design (one of my alts has black-tipped ears) and some are affected by the highlight colour, but they're tied to the specific designs and you can't choose them independently.

It's very unlikely that they would add a completely separate colour choice at this point. The character creator doesn't seem to get updates beyond extra hairstyles, but also it makes logical sense for them to be the same colour - fur and hair are the same thing essentially, and the same colour is applied to both. I think they would look strange if they were different colours.