I have an 06 Impala LT that looks like it's leaking coolant near the front passenger door. I noticed it this morning when I saw a wet spot on my driveway. I didn't see any oil/transmission leaks but I am not 100% sure that it is coolant (looks light pink). It looks like the small bleeder valve on the bottom left of the radiator is leaking.
The first thing you will need to do is confirm where the source of the leak is. You could rent a pressure tester that forces pressure into the system or just let the car run until it's warmed up enough to be fully pressurized and closely inspect where it's leaking, but you'll want to wipe the entire area down thoroughly first. Using a pressure tester will keep everything cool in case you need to get your hands down in there to help identify the leak. Letting the car run will give you pressure to help in trying to identify the leak, but obviously everything will become pretty hot around the area. Again, wipe everything down thoroughly before either method. Once pressurized, start from high up and carefully check for steam, sputtering, bubbling or other signs of leaks and work down to the petcock valve area. Be sure to check any hoses above this deposit point to make sure that's not the source of the leak. If you can't get a definitive answer with the radiator in, you may need to drain it, remove it, and carefully inspect for cracks/damage after pulling the entire unit out. If you're still unsure, you can bring the radiator to a place that offers a pressure test on the unit while out of the vehicle. Now, if the leak is coming from the petcock valve seal or retaining clip, you can check to see if there's a kit available to replace the assembly, price it, price a new radiator and do a cost-benefit analysis. Also check the condition of the radiator to see if it should be replaced anyway and take that into consideration. There's no guarantee that replacing the petcock assembly will be successful for you and, if not, you've paid for the kit and then may need to purchase a new radiator anyway. If it is successful, you may find that you've saved money. That's just a decision you're going to have to make yourself. If the source of the leak is on a flat surface of the radiator somewhere, some have had success using an appropriate J.B. Weld compound (depending on what type of surface you're dealing with), but I personally would recommend full replacement instead. Finally, if the leak is not on a flat, accessible surface then full replacement is needed. Here's a link that may help with petcock assembly replacement: https://m.carsdirect.com/car-repair/how-to-fix-a-leaking-radiator-drain-petcock
I'll be honest though, there may be coolant leaking out of the actual drain, but the presence of fluid around that seal suggests it's coming from actual damage somewhere. It's just a matter of finding out where. If it were only leaking out of the drain then I'd suggest making sure the valve is completely tightened (without over tightening) and if that didn't work, I'd be more confident in replacement of the petcock valve assembly. But based on the pictures, it looks like it's leaking from somewhere else, not the drain (or at least not only the drain). Hope that helps. Good luck.