JCPenney Special Run
#711096 12-Piece Stablemates Set
If you were bound and determined to make this model a pure-bred Arabian, you could make a case for flea-bitten grey or maybe Breyer-style rabicano, but this mare is about as close to true roan as any of the 'roan' Stablemates out there.
If you decide to go with black (often called 'blue') roan, you'll have to find another roan-carrying breed for her non-Arabian cross. On a whim I made mine a Paso Fino x Arabian, but just about any relatively light breed with roan will work.
A little trivia for you, there's only one other black G1 Arabian Mare out there - the solid black model from the 1990 Sears SR Stablemate Assortment II.