When I cast {Manamorphose} when do I have to choose what colors of mana to produce? And can I draw a card and then choose the colors? I don't think so but I would love clarification...
When a spell resolves, you have to follow the instructions on the card in the order written.
You don't have to announce the colors when you cast the spell, but it is the first thing you do as it resolves before you draw your card.