Update: The Clarke patch of June 1 solved the problem.
It seems that once you have built a colony ship, there seems to be no way to check which species it transports from clicking on the ship. This isn't a problem early in the game, when you have just your starting species, but later, you build lots of colony ships in lots of places, and it's be nice to click on a ship and actually see which planet type it can colonize.
My workaround right now is remember the ship's name, click any planet, click the colonize button in the planet UI, and find the ship in the resulting list.
Is there an easier way?