Is it too late once you find rust in coolant? damage? coolant is a year over due.

 

Just drain the cooling system, flush it thoroughly using a garden hose, and refill it with the coolant recommended by Ford.
You didn't mention which engine you have but if it's the 4.0 V6, the rust could be from the cast iron block. Otherwise it could be from the water pump impeller so it might be a good idea to replace the water pump while you're there.

 

its a 2013, did ford change coolant color to yellow? cant find parts anymore

 

It would have been helpful if you'd mentioned the year and model of your car in the first place. Anyway, I'm not sure what color of coolant was used in the 2013 but I believe it was red.

 

dude its in my signature, its always orange for 05+ mustangs i believe

 

Nope. Yellow for 05-09.

 

You're correct in so far as the Motorcraft Orange is recommended for the '11-'14 3.7 V6 & 5.0 V8. However, the '05-'10 GT requires Motorcraft Gold.
FYI, the signatures don't appear on my smartphone.

 

Orange has been discontinued and replaced with yellow. The Ford dealer parts guy said the color didn't matter anyway. Just as long as the coolant is approved to be used in Fords.