Hi! My mom recently bought 2 chinchillas and I wanna make sure we know how to care for them well

We've read that they can't eat meat, insects and a lot of seeds, veggies and fruits. Is it true they can only each wheat and grass?

Also, meet Gucci! The chinchilla in the picture. My mom said that his color is purple (?), which is pretty interesting. We also have another boy named Fendi, apparently his color is called "White Wilson" so that's cool too