Like many people at this time of year my neck is lighter than my face
because the sun doesn't really hit my neck. Rather than choose a lighter
foundation shade to match my neck (which tends to make me look ill and
needs significant bronzing up) or use a darker shade which might result
in a tide mark along my jawline unless I blend my foundation all the way
down my neck, I just put a lighter shade of foundation along my
jawline. I then use the shade that matches the rest of my face on my
cheeks, nose, forehead. I can usually blend the two areas together
seamlessly. It also has the effect of sculpting the jaw slightly,
partiularly if you apply a contour shade underneath the jawline. I don't
usually have to buy a lighter shade of foundation, most of us have a
summer and winter shade of foundation, or I use samples of foundation
that were too pale for me.