I think it's this one. They have a team of sentai villains that goes 0, 1, 2, 4. It makes sense that there would be a 3. And that he would be one of the missing colors(either Black or Yellow).
It's just serendipity that they went with the color that's already associated with Sanji, and the power that he always wanted.
I would buy that...if Sanji didn't have a wanted poster. And is in no way disguising his face as the soba cook. Literally ANYONE should be able to see Sanji and know who he is. That's the entire POINT of a wanted poster.
Now, I could buy that maybe this particular guy doesn't pay attention to wanted posters, but anyone in Kaido's organization might, so not having an ACTUAL disguise is...I just don't get it.
At least Usopp wears a fake beard.
And that's ignoring the fact that all of them have their real names IN their fake names! Again, the names that are on their wanted posters!