You will want your kitchen and bath styles to be the same, whether traditional, modern, rustic, etc. but you can absolutely use different materials in each room, or go more transitional in one of the rooms. You also want the colors in each room to coordinate with whatever adjacent room it connects to.

As Calidesign said, you want all of the rooms in a home to feel like they belong. So in terms of style (modern, traditional, etc.) they should coordinate. As for materials, they can be completely separate.

Ok so I guess I’m overthinking it. I’d say my house is coastal transitional with a touch of rustic. The bathrooms have almond ceramic tile counters and a cute sea glass/stone backsplash and the master has travertine counters and a similar backsplash. All of our house has the same espresso-stained cabinetry. So using white or almond subway tile in the kitchen works? I was wondering if I should add some of the sea glass (like a strip through the subway tile backsplash) to coordinate with the rest of the house?

You're overthinking it. Just take a deep breath. If the almond/white subway tile works with everything else in the kitchen then go for it. It's hard to say without seeing it, but I'm not a big fan of accent tiles in kitchens. I'd skip the sea glass as that feels like it's trying too hard to be matchy-matchy.

This is the kitchen

I was thinking something similar to this

That glass tile detail is what’s in our master Bath.

I just don’t want the kitchen to look too farmhouse-y (even though that’s what I love). I want it to still fit with the coastal vibe. We have rustic dark wood floors and coordinating barn doors that close off our formal fining and a wood valance in the kitchen.

Almond/white subway tile would be perfect in your kitchen, without any accent tile. Pick at color that matches the lights background of the countertops. You've got a lot of variation in the countertops, so you don't need anything more for the back splash. Be sure to remove the current short back splash before you add the subway tile. As an aside, you can use a dark brown outlet cover to replace your white one on the side of the island.

Skip the accent tile. It adds nothing.

Perfect. I didn’t want it anyway.

You guys are the best.