Orange is usually Dexcool, which is not good for your engine and cannot be mixed with any other antifreeze.

I suggest ordering a gallon of Volvo AF or buying a gallon of Zerex G05. Then get 3 gallons of distilled water at your supermarket and save a couple of gallon milk jugs for recycling.

Remove the splash pan under the car to make things easy. Empty the radiator and then loosen the bottom radiator hose to drain the rest.

Because a pint or so remains in the heater core, add two gallons of water through the overflow bottle, burp the large hose a couple of times, start the engine and run it for a few minutes. Flush again

Then pour in the antifreeze and top off with water. Burp the hose. Top to max. Start and run engine until the radiator fan kicks in. Let the engine cool and check the level.

Of course, you are also doing the Tbelt and pump. So I suggest you drain and flush before removing the pump. Makes things cleaner when taking out the old pump.

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Keeping it running is better than buying new

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