It is hard to know what is going on without knowing a bit more about how the scar looks. I suspect that what you mean is that they area where the shingles was is a bit lighter than the surrounding skin. If so, this is a very common problem that is basically an extension of the normal healing process in the skin, called postinflammatory hypopigmentation.
Postinflammatory hypopigmentation, luckily, will often fade and disappear over time, but this can take months to years for the pigmented cells to move back into the area and smooth out the skin tone. There is not, unfortunately, much you can do to speed up the process. Occasionally sun exposure or tanning will help to darken the areas a bit more quickly but this is unpredictable and brings along all of the problems of skin damage associated with these activities.
Although many toning creams are sold over the counter, these are generally expensive and ineffective, and they are probably not worth your while.
Therefore, your best bet is simply to wait it out and expect it to improve slowly over time. You could talk to your dermatologist
if you have further questions or concerns about the issue.