User blog comment:Omega natsu2/Chapter 372: Breach, Predictions./@comment-198.142.230.138-20140219084258/@comment-7418318-20140220100424

Especially in a world where transformation magic is quite common, thus allowing a mage to have his or her eyes appear pretty much any way they like for very little magic power costs.

Also Jiemma didn't have black eyes. In many shorts his pupils aren't shown (i.e. completely white eyes) but in others you could see the pupils, like in, so I'm also sure that Jiemma was not a Demon back during his time as Guildmaster (and neither was Jose).

Though considering how his daughter was turned into a Demon, he might also have become one during the time we havn't seen him, but I doubt it.