I see, the goalpost just moved further away.
Shadows created by light or for effects like being angry, epic moment (shadows over eyes), make things more dramatic etc. Not a single one of these was at the same Situation as Sanji. Sanji was Blocking an sharp attack in form of arrows. Sanji having ''shadows'' on his neck and cheek make Zero sense - why should there be any of those shadows? But on the rest of his face, like his eyebrow - where normaly shadows are created is none.
The arrows which hit Sanji got
deflected and there is only 1 thing in OP that is black and harden your Body - it isn't so hard to guess what is is right? It's a big ''coinsidence'' that the parts of his Body which are hit by arrows are black and the parts which are not hit are white...
I have the Feeling some People get butthurt for Sanji having Hardening - so they try everything to ''disprove'' it lol.
Well, then i guess Sanji has the hardest body of the SH's (besides Franky).