My new addition Alfie (a large Campbells male from the animal rescue) has slightly sludgy green diarrhoea. Not profusely, just a small amount - it's not watery, more like a thick paste, but it is bright green!
The rescue say they have not fed him any fresh food in the 2 weeks they've had him, but they are going to check with all the volunteers that work there just in case. I can't think of anything else that causes green diarrhoea apart from too much green food!
He is fine in himself apart from that so I am going to treat it as dietary/stress-induced for now - keep an eye on him, make sure he's taking in enough water (which has probiotics in) and only offer dry food.
If any of the experienced hamster keepers here have any ideas about what else might cause it to be green, let me know!!! The only other green diarrhoea disease I can think of is Newcastle disease in poultry, I'm certain it's not that!