Can I switch sim cards between 2 Iphone 4s?

I just got 2 iphones from telus and they are both signed up under my name. I got a black and a white and my fiance and I would like to switch colors. I don't have much experience with smartphones at all so I just wanted to know is it as straight forward as switching our sim cards or is there anything else we need to do?

Just switch them - the day my account got cancelled i put my boyfriend activated sim card in my iphone - come to think about it i don't remember what happened to my old sim card lol