My temp gauge is stuck on lowest level and the engine mgmt light is lit, was told it could be the coolant temp sensor

So looked at the DIY's and it looks a straightforward enough job, bought the part (was told to make sure I got the green version of the sensor and not the black)

Now here is my problem, when I got the connector off the one in the car it only has two pins? The one I bought has four? Had a quick look on th Internet and it appears that all the two pin sensors are grey and not green? Is this correct? And more importantly is it ok to fit a grey one?

Thanks in advance