I feel a black cabinet with gold fixtures would work with the travertine floors. In my opinion I would be careful selecting counter as you don’t want one that has a cool tone. It would be a good idea to update lighting first as that can make a big difference.
You didn’t specify, but are you doing changes to shower too?
https://www.houzz.com/photos/modern-farmhouse-bath-1-farmhouse-bathroom-phoenix-phvw-vp~161253893

Thank you for replying. We’re not changing the shower (it’s all travertine also) but we will change the fixtures. The link you sent is stunning, they do however have a window which lets in a lot of natural light and it doesn’t have an upper cabinet. Maybe the upper should be white? I wish I could see it!

MarleneM, I only got a part of your 2nd comment! It stopped at “you don’t want to”... I don’t know why it’s not showing up here

Amanda, I agree that’s a beautiful bathroom! Since you aren’t changing the shower I feel it’s best to go with choices that work with both that and the floor tile. Look into griege colours that lean warm. Pick a medium tone for cabinets and lighter tone for walls, that way room would glow better and not look like you only updated half of room. Also wall cabinet would kinda blend in with wall. The colours in photo below represent this, and also notice the veining in countertop appears to be a warmer brown tone.

https://www.houzz.com/photos/part-3-before-and-after-en-suite-bathroom-renovation-in-brantford-transitional-bathroom-toronto-phvw-vp~164522174