I had my black 920 replaced for battery issues. They didnt ask what color i had, I just assumed that they knew. They sent me a new black 920 in the mail 3 days later and i just swapped the sim card and put my old one in the same box and mailed it back. Pretty seamless process.
And I have to say the set up process from my sky drive backup on the new phone was awesome. even downloaded all of my apps. All I had to do was move my tiles around on my home screen like I had them. Took 15 min.