𝐃𝐨𝐠 𝐕𝐨𝐦𝐢𝐭 𝐂𝐨𝐥𝐨𝐫 𝐆𝐮𝐢𝐝𝐞
These are the most common reasons, but check with your vet when in doubt.
Clear: stomach secretions; drank too much water too fast
Yellow: empty tummy; bile secretions
Green: ate green coloured foods/grass
Brown: could be due to food in esophagus when dog eats too fast, eating poop
Red: possible internal bleeding
Black: dog ate mud, possible obstruction, internal bleeding
(Saved from Monica Segal)