LOL, it turns out there are all sorts of "color changing cups". I was amazed by the variety I found on Amazon.
I looked at the box (dogs don't do much wrapping) and mine came from here:
https://www.gizmoapparel.com/
edit/ps: Buddy the dog is on his last legs... I will be sad to see him go but as I say, despite being my dog and I love him, he isn't much of a dog! He's a loyal companion but always a snacker of "kitty rocas" as we call them around here
We had to devise quite the maze that allowed the cat to get in/out the cat box as he got older and still kept the dog out.