Yes, rabbits can eat cauliflower as a treat. As long as it’s raw and has been washed thoroughly, your adult rabbit can have one tablespoon of cauliflower for every two pounds that they weigh. As a treat, your rabbit can have cauliflower at most twice per week.
Rabbits can safely eat green, orange, and purple cauliflower. All three have very similar nutritional value and your rabbit will have no trouble digesting them.