Well I haven't watched Afro Samurai but from what I'm getting is that they are talking bout the Color or character design...
Anyways if it is just Character Design Vs the back drop .. meaning if you insert the type of coloring of the type of characters from Bleach into Ergo Proxy or Gilgamesh then that would look totally bizarre ... and in the same context, if the Characters of those animes were inserted in Bleach or Naruto colored Animes then that woul equally seem Alien :P
So every anime needs to have its own type of Design regarding its theme...
Yes you could make the whole Bleach anime into the less-colorful type of animes or Dark Themed colors, but then that would give it a totally different appeal than its current stucture .
Well if that doesn't answer the Question then I'm sorry, I just might not have got the full meaning of the Question asked :m-bata: