This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Orion script was commonly found at Orion establishments such as the Orion embassy outpost on Qo'noS and the Orion Syndicate slave auctions on Verex III. (DIS: "Will You Take My Hand?", ENT: "Borderland")
While being held by Orion guards, wrapped in chains, in a prison cell, suspended from the ceiling, Harcourt Fenton Mudd sarcastically scoffed: "Is there a word in your language for 'overkill'?" (ST: "The Escape Artist")
When the Emerald Chain commandeered the USS Discovery in 3189, they replaced the operating system with an Orion one, causing all consoles and displays to provide information in Orion. (DIS: "There Is A Tide...", "That Hope Is You, Part 2")
The Orion script used on Star Trek: Discovery correlates directly to Roman alphabet letters/numbers and can be "translated." 
The Star Trek: The Role Playing Game (FASA) produced a two-book set, The Orions: Book of Common Knowledge and Book of Deep Knowledge, that described Orion culture and language. Other novels have since described a number of Orion dialects, including backcountry (Crossroad), trader's tongue (Prime Directive), Yrevish (Red Sector) and Orion Prime (Star Trek.)