It is definately just a colour....
And not all Calicos colours look the same.
I have enclosed a pic of my Calico Phoenix.Mind you she is a longhaired.And she is very petite.She even has a petite tail..LOL
My sister has a tortie named Muffin.
Here is a pic and some infor on Torites.
http://www.vegasthecat.com/about.html