Heh! Well, since I’ve been babysitting my brother’s chocobo, I’ve noticed a few BIG differences in appearance between my red chocobo and his black chocobo.
Really, they look obviously different that you could tell at just a glance.

ArashiZetsuei (red) is a Digger Chocobo. She currently has First-Class discernment.
ChocolatCiel (black) is a Runner Chocobo, currently First-Class in both Strength and Endurance.

Of course we can see the beaks….that really stand out in contrast.
Arashi has got a pair of beaks that look as if they can slam through a Galka’s skull >.>
And the feathers on the head also look bigger, thicker, and longer.

Well, both of them have large eyes (I’ve seen other chocobo with noticably narrower eyes) but ChocolatCiel’s eyes seem a bit rounder?

Next, the legs and feet. I can’t see any difference here except for the skin pattern. The size looks identical, right?

Then, the butts, oops, I meant the tails!

Look! His chocobo has more tailfeathers then than mine!

Let’s see these tails closer…. in a better angle.

ChocolatCiel has 3 layers of tailfeathers while ArashiZetsuei has only 1! Not counting the short layer extending from the back towards tail though.

This is fun XD I wish SE had made chocobo’s appearance more various than this, and I’d like a purple (I mean real purple, not bluish) chocobo!