From the very beginning we have debated whether or not to make the initial stick optional. We wanted at least a semester of code to review before we made a decision. I personally lean toward making it optional and just have to persuade the others (-:. With that, you would be able to write

data Color: Red | Black | Green;

We did also initially discuss using = instead of : in places where we were defining things (functions, data). That's still not completely out of the question. That would get you to

data Color = Red | Green | Black;

We need a closing delimiter to avoid creating huge ambiguities in the grammar.