A. This could be many things, however first I'd ask you (if we could talk) if your puppy is vaccinated against parvo? That's a serious viral disease that produces very bad-smelling bloody diarrhea. If he's not vaccinated against parvo, please take him in to see a vet right away.
Otherwise, if he is vaccinated against parvo, he could have intestinal parasites, he could have eaten something that's upset his GI tract, or he could have a bacterial infection, for starters. The orange color you mentioned has me especially concerned - I'm worried it could be blood. Regardless - he's not eating, and he's lethargic, so he likely feels pretty awful. I recommend you take him to see a vet right away who can figure out what's going on and treat it appropriately.
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