My 3 year old has green, yellow very pale poo. Never brown. Like this for months!?

My 3 year old always has pale pooh, varies from pale green to yellows and tonight yellowy white. he is healthy and happy. Eats a varied diet, enjoying meat, vegetables and fruit as well as occaisional sweets. Drinks large amounts but always so.......It has been like this for nearly ayear. His weight is good for his height. He is tall for age