Could be dietary...green tinted runs is from too much grain/graze/wet graze...
did he get into anyones feed? Introduced to new pasture?
Could be worms...dark brown to black...
have a fecal done to see if your wormer worked...check his lower inner eye lids for color..should be deep pink to red
Take his temp..shouldbe 101.5-103.5
Stop all grain...give pepto ..give cd antitoxin...offer electrolytes to keep him hydrated...here is a great recipe
A half gallon of hot water
2-6 Tablespoons of Unsulphured Blackstrap Molasses or what you have on hand or honey
1-2 Tablespoons of Either Sea Salt, Epsom Salt, Baking Soda or Table Salt.
1 cup of Apple Cider Vinegar
Mix well and drench or let them drink it.