Yes, two varieties of the same species, Phaseolus lunatus.
Hawai'i is an expensive place to buy food, but frozen, Fordhook Limas, Baby Limas, and Butter Beans are available. Both Limas and Butter Beans are available in cans and dried.
I've grown different varieties of Limas (some purple) and they taste great. I've yet to grow Butter Beans. The season to start them is now!
The main difference I can see in stores is Limas are green, and Butter Beans are beige / whitish. They both vary in size.
