Ensuites need to be the same style and color palette as the bedrom they are connected to but a hal bathroom can be what ever you want it to be. The other 2 are never seen togehter so they did not need to be the same either .

Do something special for the guest bath.

You're about to find out that there are a lot of different opinions on this. :-)

Usually the only time all bathrooms look the same is when they're new. Already there are two Pros stating they don't need to look the same. Here's my theory. I like to do something elevated in the master bath because that's the bathroom I use and it's the most important one when you go to sell. If you have children, their bathroom is a place to have some fun. IMO, a guest bath should be fairly neutral, although you can see Beverly thinks it's a good place to do something special. However, I do like to have some commonality in all of them. I just moved to a new (to me) 25 year old house two years ago. I remodeled the master bathroom last year. It is gray and white. I may not get around to doing the other bathroom for a while since we're empty nesters. At the moment it's all white, but I painted the walls blue. If I were remodeling it I would also do gray and white, but not in the same amounts. I would use the same floor tile, but in a different size. I wouldn't put marble countertops in a hall bath, but I did in the master bath.

If you live in an area where there are dedicated tile stores, or a large flooring store where they sell tile, I encourage you to work with one of their designers. They can help you do something that is coordinated, but not the same in all of your bathrooms. I have remodeled four full bathrooms and two powder rooms in my lifetime and I always go to the same tile store. I do have a concept in mind, but they always help me pull it together and suggest things I never would have thought of. You don't get this type of service in a big box store. Sorry to go on at such length! I hope this helps.

I have a hard time envisioning your new cabinet style (very pretty and contemporary) with the vintage looking yellow tile is the guest bath (which I also like very much). The guest bath certainly does not have to coordinate with the other baths, but it does need to be compatible somewhat with the rest of your home. You don’t want guests to feel they’re stepping onto another planet! Since the tiles are in the vintage style, maybe see about something that leans more towards the mid-century modern.

Are you trying to coordinate with the yellow tiles? I would try to make the three bathrooms at least look like they’re from the same era. The yellow one is the outlier. I agree it can be more “fun”, but your taste is subtle, so I would mimic some of the other bathroom elements and use fantastic wallpaper in this one. Loads of fun peel-and-stick wallpapers on Spoonflower.com. Even if you keep the yellow, that website’s papers can elevate the fun-factor.

When we remodel the guest bath we would not save the yellow tiles. We have a mid century ranch style house and will stick with that look overall. The wallpaper in it now is peel and stick.