if you can see a chade difference between face and neck, you are using the wrong shade and maybe the wrong texture.
You need matching.
At a counter they use 3 swatches of colour. The one that blends into your bare skin the best so you can't see it, is the right shade. You can also try a swatch of colour on your neck .
By 'swatch' I mean a small blob of foundation, blended in.