Bear in mind some antifreeze brands are actually orange - as it does come in all sorts of lovely colours (orange, red, purple, blue, green etc). But it should remain transparent.
However, the fact the engine overheated and had ran low on water on a k-series engine almost definetely means head gasket damage, I'm afraid.
Usual cause of this is leakage via manifold o-rings. And occasionally a water pump leak (amongst other things).
get the car down to a garage and have the cooling system pressure tested asap.
Last edited by ALi-B; 11 November 2005 at 12:28 PM.