The orange stuff?? I guess that means you still have the stock Dex-Cool in there. Some people say you shouldn't mix Dex-cool with other kinds of antifreeze, others say it shouldn't matter. Just to be safe, I'd stay with Dex-Cool, unless you want to completely flush and refill the system.
As for locating the leak, 84fiero's clean cardboard trick is a good way to start checking for leaks. Pressuring the system up (cold) with a pressure tester (Autozone has these in their loan-a-tool program) may accelerate the process of finding the leak. I think I would also check the oil and make sure there's no coolant in the oil, just in case the leak is internal instead of external.
As for locating the leak, 84fiero's clean cardboard trick is a good way to start checking for leaks. Pressuring the system up (cold) with a pressure tester (Autozone has these in their loan-a-tool program) may accelerate the process of finding the leak. I think I would also check the oil and make sure there's no coolant in the oil, just in case the leak is internal instead of external.