like the others have said, you need to have your original ring replated. all gold is yellow. they change the color by adding other metals to the mix. white gold & platinum are generally plated with rhodium. it will wear off eventually. platinum is a white metal, but it's dull. they plate it with rhodium to make it shiny.
I like both rings if you decide to get a new one. the tiffany will be easier to wear with an engagement ring. you'll have to try the trinity on with your e-ring to see if you like them together.