Choose a solid grayish/tan/taupe color mat that will blend with the floor

The one with white diamond tiles I would get white mats and towels. The other look for a cream color.

Tan mats. Macy's has good quality nylon mats.

Do you have or are getting shower curtains and towels; when adding anything new, it shouldn't be chosen without considering the entire space Without seeing the rooms, suggest a simple white mat with a slight texture (which can be bleached to keep fresh), sure to chose the appropriate size, and that it works with towels/shower curtain.

Just a minute ago I bought a washable rug from the Amazon Prime Day deals. The brand is NuLoom, design is Mae. Comes in three colors. Reviews are great, so that encouraged me to give the rug a try. I got the runner for my slider by the pool. These are indoor only rugs.

There are customer. photos, and couple were of the rugs in bathrooms.

I got the gray and it might work for you, too, and looks like it would work with Maureen's suggestions, as well.