I'll take a stab, but I am probably out of my league here...
Cet marcach do, ti dubglas co luban airgid im leith in dirma
First(?) a horsemen...(sorry, don't know what "do" is here), dark-gray
cloak (tí) with a multitude of silver tassels around one side/half
7 lenda corcrai ima leith n-aill co cortharaib oir 7 airgaid.
and purple mantle around the other side/half, with fringes/borders (if we
read *cortharaig) of gold and silver.
Ech dubglasa fo leith in tluaig, gabra geala fon leith aile.
A dark-gray horse separate from the host. A white mare on the other side.
- Chris Gwinn