Sorry, I don't really understand what you mean. Do you mean the outline around the curve of the neck - how its really dark?
Wether it is dark or light isnt really what i was trying to address, but rather the fact that you have used a continuous line of solid colour to outline the edge of the neck.
Zoom in on my example and make a comparison. Instead of using solid lines, I have used shadowing/shading to define actual
depth.
I'm horrible at explaining things which is why I make examples in the first place haha. The only thing I can suggest to you is to actually take a good look at the example and compare.