That was my problem.
I didn't know which color I should pick from the reference as it's pencil colored.
So much gradients in the drawing/coloring, hmm okay I think I may be able to fix that. If not, I am so sorry.
How this looks? If it's still dark for you, I am so sorry in advance that I can't brighten it anymore cause I'll look super weird if I brighten a little bit more. That's white-brighten of 10%. Anything exceed that percentage would lead the piece to become really weird and white.