So as Marcie mentioned, you can create these in SFDC and create the sync... if sales needs this information on the pages.
But if you just need the info for marketing/event/etc purposes you can just keep in MKTO. Your new field would be "Favorite Color" etc. Just name well so you can tell what the field is and reuse, you can't change the name of it later.
Then in the form you'd change what the display text reads as, so in this case "What is your favorite color?". Use Forms 2.0 and it's pretty easy to use -- changing text and answer type. Let me know if you have questions when making the form!
Kim