he's at Mt. Silver.
Mt. Moon is about the size of a shoe-box, and there really isn't anything hidden in there.
you'll need flash to get through Mt. silver if you're on gold, silver or crystal, and you'll need rock climb if you're playing heart gold, or soul silver.
Red is not in Mt. Moon; he is at the top of Mt. Silver.
Red is not available to be found anywhere after you defeat him in your battle against him within Mt. Silver however Red will reappear in Mt. Silver if you challenge the Elite 4 once again and defeat them as well as Lance.
After you defeat red he leaves to Hoenn I do not know about that , but to rebattle him again, you must defeat the Elite 4 (or shall I say 5) again. Then he will probably be back on the peak of Mt. Silver.
Mt. Silver after you defeat Red (A.K.A. Ash) who is also somewhere in Mt. Silver
You win this badge when you defeat Red in Mt. Silver.
After you defeat Red ( who is in mt silver ) Boaba will call you and give you them
You beat red in MT. sILVER
You have to defeat the Eight Kanto gym leaders before you can fight red. After you defeat them you can go after red, he is at the top of Mt. Silver.
You defeat Red on top of Mt. Silver. Talk to Mr. Pokemon and he'll give you the blue/ red orb.
somewhere....... to defeat him again, you have to beat the elite 4 and he will be back in mt. silver again.
After you defeat both champions you can go to mt silver go there and you will find him.
I don't know where he goes, but you have to defeat the Elite 4 (or shall I say5), again for him to reappear at the peak of Mt. Silver.