So my sister's 2016 CX-5 threw a CEL and when I scanned the codes, it had some misfire's in Cylinder 1. I figured a good place to start was probably to change out the plugs since she has 65k miles and they're starting to get old. However, when I pulled plug 1, I found that the whole well was filled with bright green coolant. Now, I don't believe that this is a head gasket because the oil and coolant are completely clean, not mixing, not milky, and the cylinder was dry; it was just the plug well that had the coolant. The spark plug was also not fouled, but the threads were wet and got drier towards the tip. I noticed at the top of the well at the valve cover gasket that there was some moderate corrosion, but coolant doesn't flow through at the valve cover, so I'm not sure what that is about.
In my mind, I'm thinking that the car probably has a crack in the head. Does anyone else have any fixes or explanations, or better Mazda knowledge and know what this is? It is also important to note that only cylinder well 1 had coolant, all other wells were clean and dry.

Thanks in advance for your help and suggestions.
Attached are a few pictures.

Green coolant in the plug well.

Cylinder 1 spark plug.

 

I've been working on CX-5s since their launch in 2012, I've never seen this.

What I would do is clean out / dry out all the fluid, warm up the engine, pressure test the cooling system for several hours, and monitor for any leaks / appearance of coolant around the spark plugs..