I'd say most likely a blown/leaky HG, discolored radiator fluid probable due to air getting in from the blown HG. Could also have a cracked head which would do the same kind of thing. If your so inclined, you can check for a blown HG by using a compressor to pump air into each spark plug hole,(need a good seal), remove the radiator cap and watch for bubbles/leaking fluid. It could also be a leaky/faulty water pump..you said you were re-filling so I assume your losing fluid. Temps still high?