My truck has what looks like transmission Fluid in the radiator i have not seen any leaks but my water res is all pinkish how is that possible and how do i fix it

 

If,,,,,,,,,, it is trans fluid , it might have come from the trans cooler in the vehicle radiator.
If,,,, it is trans fluid, it is under higher pressure than the 15lbs of the cooling system.
The problem is; when the vehicle is shut down, trans system fluid pressure goes to zero, but the cooling system will still have some pressure until it cools down. Now there is a possibility for coolant to get into the trans and if that has taken place , the trans components do not get along well with coolant and a trans overhaul may be in the near future. Don't wait !!!! Get it checked out ASAP.