My aim is to paint realistic skin tone. Please help.
Oookay there is such a thing as putting TOO many colours in your skin tone pallet. Skin has greens, yellows, and reds, but one of them is usually mostly dominant. It also depends on the lighting... Also if this is a man-- You might want to give him a squarer chin and bigger eyebrows... if it's a woman, try removing the adams apple that seems to have appeared. :9
But yeah, I'd say just simplify your colours a bit more.
Yes! The colours are still getting too muddy in the dark areas, I think!