Bone

Red bone

Blue bone

Green bone

You can purchase bones or red bones from Costolot's General Store. Diggerlings can dig up blue or green bones from a mine.

You might not pick a bone as a treat, but there are some piñatas who like nothing better than to gnaw on one. I think you can guess who that might be?

Uses

Tips for finding blue or green bones

Since there are many different items that can be dug up from a mine, it may take several/many in-game days before a Diggerling discovers a blue or green bone. Hiring up to four Diggerlings and paying them to increase their happiness may shorten the time it takes to find one. Note that many bones may be buried in a garden, and it's possible for more than one of each color to be dug up.

The TiP Trade forum is a good place to ask for, or sell blue and green bones.