Tiffany connotes an ‘upscale’ image so, of course, you want your favors to portray that. Steer clear of anything ‘cute’ - that is definitely not in the realm of “Tiffany”.
If your favor is being placed inside a favor bag or box putting it in a Tiffany Blue bag or box is a must. How you decorate the box is up to you, whether with a white ribbon, black ribbon, monogram tag, etc. Of course edibles inside a favor bag or box are always appreciated. And although the blue may not be a perfect match - there are plenty of blue candies available.
Unfortunately Tiffany favors are someone limited but take your time, search the net, and you will find interesting and unique favors such as miniature Tiffany cake favors, candles colored in Tiffany blue, and personalized Tiffany Blue candy wrappers.