Petunia Genetics help for potential cross

I'm trying my hand at breeding the two petunias in the pictures. The purple one is called night sky and, I think, the pink one is called pink star.

I've completely forgotten almost everything I was taught about punnet squares and I think these are codominant genes which makes the application even more confusing for me.

Is it possible to tell whether these are codominant jusy by looking and is it even worth trying to figure it out with a punnet square or should I just see what it spits out?

I've never done any actual breeding before and I'm finding this kind of exciting. Sorry if this is wildly foolish.