Orange Coolant Turning Green 1.6 Ecoboost

[MJS09]

Hello,

I recently had the 17S09 recall work done on my Ford Focus 1.6 Ecoboost. (Still waiting for the Pcm update).

3 weeks later I had a coolant leak which was fixed by my local Ford dealer. They found the leak from a pipe connecting to the thermostat. 

I have been checking my coolant daily since then and have noticed that after a journey, when the engine gets hot, the coolant turns green as shown in the photo below. A couple of hours later once the engine has cooled down, it goes back to being the normal orange colour. Since ive owned the car its always had orange coolant and never had this problem until recently (After the recall work).

Has anyone had this issue before or can anyone shed any light on what it could be? Fyi I have phoned my local Ford dealer to ask the question and they have never heard of this issue. Before I take it back in I wanted to see if anyone has encountered this on their cars?

Any help and advice is appreciated.

Thanks