Wondering what may be causing it. No changes in diet that I am aware of. She's a 7-year-old 30-lb Chihuahua mix/rescue from Puerto Rico, we have had her since she was 3 months old. No behavioral changes, she's peppy, racing around on walks, cheerful, normal appetite. It's been green for about a week - not black-green or brown-green or greenish... it's bright green-green! Normal in all other aspects. I am restricting her to one simple brand of dog food through the weekend with no special treats, if necessary I will call the vet about it on Monday.

Here is Peggy Sue relaxing on the bed:

Susan