Slightly Lighten up shading on bigger surface

hi Guys, just wondering if anyone has an advice for me. for lightening up a the shading. not removing, not blurring it! I have recently got a Shield/Armor plate design on my upper arm. Since initially I did not think of getting a full sleeve design, we discussed with the guy the keep the insides of the armour plain and shaded so it is well visible from far. However you know how this works once you start you can't get enough, and now I am getting my full sleeve done slowly piece by piece. The problem that I have is that now being part of a full sleeve I would like to have the armour with the inside "engraved" and thus I need to lighten up the shading a little. it's now been quite a while since it has been done, perhaps 2-3 months, and still the nearly black shaded parts still seem to be glossy ( so perhaps they are not even healed yet, but that seems strange after 2-3months. ) I love the tattoo, but I would love to add a little extra design like engraved acanthus leaves on the surface but for that I would need to lighten it up a little. Laser will probably not work I guess, and I am not sure if these creams advertised on the net will help out. I have tought of white ink, or grey, but I coudl do with some other advices.. thx