House Jordayne's sigil is a golden quill on checkered dark and light green.
In the books
In the A Song of Ice and Fire novels, House Jordayne are also vassals to House Martell. They are ruled by Lord Trebor Jordayne. Prince Oberyn is accompanied to King's Landing by Lord Trebor's daughter and heir Myria Jordayne.
The name of the house is an homage to Robert Jordan, author of The Wheel of Time novels and a friend of George R.R. Martin. The lord is called "Trebor" which is "Robert" backwards. "Jordayne" is similar to "Jordan" and "Tor" is Jordan's publisher.
Houses from Dorne