Carl is dead right, it's a good idea to experiment. Apart from there being no one way to lighten or darken anything your taste in colour will determine what you think works best.
Colours like flesh can work well for this kind of thing and it's certainly worth a shot if you already have one; it should give something usable. You might need to add a little additional white for the lightest areas.
For brighter highlights you might like to try white and yellow (works well for greens too).
For the shadows you can use a lot of things depending on the effect you prefer. Many dark blues will actually work well with colours similar to this, but just black is worth trying too as are any greens you might have; all you have to do is be careful not to add too much - 1:10 might be all that's needed to give enough of a colour change for the first shadow mixture and often you'll need much less that 1:1 for the mixture that's closest to grey.
If you didn't use black, don't be afraid to try adding in a little to the last shadow mix for the darkest touches.
Einion