Erik allows Charles' interest in the small notes of his skin to an extent that 'allowance' doesn't describe; he can engage actively in absolute stillness where on others that might speak to passivity, or mere tolerance. The primary difference, besides the swift sea-change that darkens his eyes just a touch, is that Charles will sense the peaking of Erik's thoughts, the aching knots that loosen just the barest of degrees in watching this. He also thinks, of course, that as far as their respective ages stand there are certain capacities in which Charles is a boy, but if he were letting that stop him instead of just occasionally quirking wryly at it, he wouldn't be here. "I like whatever you like," he says, truthfully; he is about as practiced as using any of those words as he is flying.
Still, this is not an answer, and as close to reality as it hews Erik doesn't suffer indecision in himself or anyone else. "Don't think that I don't care, it's not that." He shifts his hands slightly and brings both of Charles' back to the bedcovers, using the other to cup his jaw, if Charles is so interesting in divining the finer points of his chemical structure. (He does smell like metal, and the fact that in many respects this is similar to smelling like blood is not lost on him.) "But I've worn a label before, it hasn't exactly turned out."
Erik can do this, the way he casually referred to his former tenure as a lab rat, and not become instantly mired in the place those memories come from; there are enough layers of lead under his skin to keep that from him. This doesn't keep him from anticipating a paroxysm of horror from Charles, whose heart is to his mind so much more easily bruised, and he squeezes their hands together tightly enough to blanch his knuckles white in an aim to prevent that. "What I'm saying is I'm not in a fit position to decide what I like, I don't object."
He does wear those names once so demonized with defiant pride, after all; he retains his mother's heritage if not her faith, and he had embraced 'mutant' with a quickness once he had a name for it. He could be proud of this, if only between the two of them. "Charles. What do you want to call me?"
His taste in jokes really hasn't gotten any better: "I can almost promise I'll answer to it."