Has he eaten anything odd? If he is very young and this has been going on for several hours I would look online for an emergency vet in the area and give them a call. oftentimes they will answer questions on the phone to determine how serious the condition is.
If you think the puppy ate something toxic (the whole green vomit thing sounds scary) you can call the Animal poison control 1-888-426-4435 it is 24 hours a day they will charge a fee, but if you think your dog ate something poisonous it may be worth it
Depending on pup's age, its so severe with young ones on dehydration, the green is bile dumping into stomach, because the stomach is empty, bile goes into stomachs to help churn the food and send on down to the intestines, this is not good.
Could have Distemper, need to know that first off, and got to go to vet...puppies showings signs of vomiting down the yellow/then greenish/brownish, need to be check for distemper,,,,,distemper can take a puppy's life...
Has your pup got fever??? Is its nose hot or warm, gums reddish or whitish...
syringe some mild flavor gatorade, only very little every 3-mins to hour till you get to vet, does the dog have loose bowel movements???
Or even its toxic/poison, a liver will get damage, and untimately the dog will loose its life unless you get to vet to receive a reversal if not too late of Vitamin K, that can restore the liver...
Oh goodness, it can be a multitude of many different issues, trying to find the problem can be a challenge, my suggestion, first go to vet, a lot of vets will let you pay out financially, you just have to call them.
And, where did you get the pup from, call that breeder, or spca, wherever pet came from..
breeders are very knowledgeable, cause they've gone thru everything...
Good Luck, and give your pet a big hug for me...
Please let us know you're okay!!! :o)
MISTAKE...
syringe mild flavor gatarade every 30 mins or every 1 hour, till you get to a vet, or the vomiting stops...depending on size,,,,,small dog, small amounts, med dog, med and so on...