first somehting i have learned about skins and colour that may help in the future:
if the skin is yellowish, avoid using blues, because a yellow blue creates a more greyed result, which makes skin feel muddy
yellow with blue light(shadow) hitting it turns greenish, this is why yellow skins often have greenish shadows...there are circumstances where it might appear more greyed, but for the basics i would avoid it
you can also use warm browns to help define/shadow the face
when the skin gets a bit more pinkish or preferably pale, then you can begin to use blues as you will find they keep their colour more and dont muddy up colours
also for the main skin tone, try to keep the colour more saturated...as skin dies it loses its colour(deaturates) and thus dead skin is more greyed, live skin is more colourful...leave the heavily desaturated colours to the shadows
the next key is the most beutiful colour appears in the highlights, so use rich colour in the highlights, yellows, oranges, and so forth(if in sunlight) instead of greyed tones or whites(unless the very brightest points)
while far from perfect heres an edit, basically what i did was soften the contrast, and avoid using strong blues, instead i used the greens, a dark warm brown, and around the eyes reds and purples in combo with the existing blues
i also tried to bring the highlights up from a greyed tone to a more elf flesh type tone...i took a lot of shadow out of the face because when looking at faces, even heavily defined ones they dont have dark shadows on the cheeks...so i softened up with reds and colours like bestial brown and snakebite....i then essentially shadowed the lower areas with a green tone, and then glazed over with the duller skin tone you have...this took the noticeable GREEN out and made it more of a \"lightly greened skin tone\"...however you could use the purples or darker browns like i used around the eyes or neck instead if you desire, instead of the greens, just avoid making it too much of a contrast
you will also notice the neck area is very much in shadow, but still has definition(it could be better but i lost my stylus so was using the mouse to colour so a bit wonky), and this helps bring the face out as long as the highlights or contrast on the chest is less than that of the face
when people say to use purples and blues, or reds, it means to add those tones, but not necessarily leave them looking red, or blue...but instead redened or blued fleshy colour...you can achieve this through mixes, or by various layers of glazes as what is underneath affects what is going on top