a6wagon

Anyone familiar with the blue drain plug on the A6 radiator. I recently replaced the heater core (ausitnaldo's step-by-step writeup proved invaluable!!!)and when bleeding the coolant system i noticed a slow drip from the blue radiator drain plug on the lower passenger side (hisis where i drained the coolant to minimize coolant leaking all over the garage duting the heater core removal). Anyone know if this is something typical? Is there an easy fix? Am i looking at a new radiator?

Any help or thoughts will be much appreciated.