I know it sounds repetitive, but for something that expensive, I would strongly suggest trying it on in person.
What is the majority of the jewelry in your collection made up of right now? What pieces of jewelry do you wear the most? Do you want it to match the rest of what you normally wear, or do you want it to stand out and be noticed?
The Cartier rose gold is not real "rosy", if that makes any sense... Tiffany's rose gold, for an example, is very pink!
I think that the yellow gold is the boldest of the three gold colors, and if you want it to STAND OUT, then get the yellow gold.
Hope that helps!