I believe that there are some titles, but I am by no means the expert on Gray Jedi. I know that forum members Karmack and TheDutchman have written quite a bit of Fan Fiction that involves Gray Jedi (I highly recommend reading it), and they would probably have a better answer for you on this.
Many of the Gray orders have adopted the ranks that appear on the Wookipedia. But for a title, the Mak'Tor simply use the term "Knight". Gray Knights, Silver Knights for more advanced, and "Sage" for the most advanced, in keeping with our association with the Song of the Maker.
To put it into a more formal format... Ar'Nor'Mack, Silver Koawan, Knight of the Mak'Tor Order. Ka'A'Mack, Meanowan Master, Sage of Song, Knight of the Mak'Tor Order.
Ironically, the title "Jedi" has become pervasive for non-Sith force users. So you have Jedi, Gray Jedi, Dark Jedi, etc... Jedi tend to refer to us as Grays. But we of the Mak'Tor refer to ourselves as Knights. :-)
Special thanks to TR and his endorsement
As with Karm, my Gray Jedi tend towards the honorifics "Master," "Knight," "Apprentice" but also include the admittedly non-canon ranks of "Kage," "Maenowan," "Kaowan," and "Teidowan" which I had researched on SWFanon. Although the rank that I incorporated into my Gray Jedi is the position of "Arbiter" an analog to the Jedi Order's position that Mace Windu occupied, basically second only to the Kage. Then, below those two positions was the Council of Balance, occupied by Gray Masters, each with the honorific of "Speaker," ranging from "First Speaker" to "Seventh Speaker" (for the 7 members of the Council of Balance).
I hope this helps/sounds interesting to you! Allow me to echo TR: I would HIGHLY recommend that you check out Karm's and TR's submissions in the Fan Fiction section. And if you're so inclined, you can read my own as well to get a better idea about the positions in the Gray Jedi