The orange stuff sounds like GM's Dexcool or what ever it was called. IIRC it does not always play well with other formulations. Not knowing what is currently in there, it is probably be best to flush the cooling system and use what ever long life antifreeze is common in your area.
How cold is it likely to get before you change the water pump ? If the temps won't go much below freezing you could safely add a little distilled water to get by until you do the work. A 2:1 mix of water:antifreeze won't freeze until 0°F.
Greg
|