Our new home will have matching counters, cabinets and floor. The master shower will have larger white tile with a large teal glass tile accent. The guest bathroom tub/shower will have smaller white tile with a large royal blue tile accent (same tile different color from master) to tie them together. The master will have the large teal glass tile as sink back splash too while the guest has the quartz counter material as a back splash. Thus they tie together but my master will be a bit more colorful.

Coordninate color schemes, sure. But to do a master "right" is going to require some updates that one might not necessarily spend the $$ for, in a guest bath.

I don't feel like they should have to co-ordinate, one's private and one isn't. Take the opportunity to do something you may have been hesitant to do in other rooms with color or the sinks or vanity or lighting. Give yourself permission to try something different.

I would chose to make them different, because they are not seen next to each other and it is nice to have the master bath/bedroom flow together. Also, half baths or powder rooms are fun to decorate, perhaps using tile, paint or wallpaper in a different way than the rest of the house. I have heard it called a "jewel box", which means it is sort of an accent room. You can often use a more expensive tile or fixtures because it is so small. You don't need much of it. Also great to have a unique mirror. Just have fun with it!

yUu can get away with them not matching, but The overall style should be somewhat cohesive. If your master bathroom is mid century modern, and your guest bathroom looks like a snapshot from Tuscany, it will feel off.