Xerxes has a 'type' - tall, dark, and brooding. They talk about this and some other preferences in a scene in Volume 1 redux ;3
Here's Ravi's reference, if I haven't posted it yet:

He's a bit older in the reference pic, because they're going to reunite in Volume 3 (he's the major character in that one, similar to Basil and Xander in Volume 2)
The black marking covering his skin is from the Sect - basically I gave Xerxes a reason for that black thing on his neck ;3
More pages very soon! I'm quite a bit of the way through coloring all these ;3