What color foal would produce if you bred a Grulla with Red Roan horse?

This is a tricky question to answer definitively without knowing the specific genetics of the Grulla and Red Roan parents. Here's why:

* Grulla is a complex color that can be produced by different combinations of genes. It's essentially a diluted bay with a silvering effect.

* Red Roan is also a complex color, usually involving the roan gene and red base color.

Here's a breakdown of the possible outcomes:

* If the Grulla is a true bay with the silvering gene (A/a, E/e, Z/Z), and the Red Roan carries a red base (E/e, R/r):**

* The most likely outcome would be Red Roan. There's also a chance for a Bay Roan.

* There is a possibility of Grulla foals if the red roan parent carries a silvering gene, but the likelihood is low.

* If the Grulla is a dilute black (A/a, E/e, Z/z), and the Red Roan carries a red base (E/e, R/r):**

* The most likely outcomes would be Red Roan, Bay Roan, or Black Roan.

* A small chance exists for a Grulla Roan if the red roan parent carries a silvering gene.

* If the Grulla is a dilute chestnut (A/a, e/e, Z/Z), and the Red Roan carries a red base (E/e, R/r):**

* The most likely outcomes would be Red Roan and Chestnut Roan.

* Grulla Roan is possible but less likely.

Ultimately, the exact color of the foal depends on the specific genes carried by each parent. A genetic test could be performed to determine the exact genes present and predict the foal's color with higher accuracy.