Chroma skins in regards to recoloring aspects.

Hi, so i'm not really a Yasuo player, but one of my friends is and I've noticed that on Yasuo one of the chroma skins re-colors his sword to gold. That made me wonder about the other chromas that are being released and why most or all of the weapons for "x" champion are not going to recieve a re-color. (I.e. The Riven chromas were some of the color schemes go completely against her sword color)