In the SYW it was part of the Army of Germany and took part in the taking of Wesel, of which it became the garrison. It was at Rossbach where it was brigaded with Salis de Mayenfeld (and where captain of grenadiers Reich and lieutenant Muller were killed, captain Dieffenthaler was wounded and taken prisoner, and "amongst the wounded" were captain Waldner and lieutenant Krefeld. These officer casualties suggest that total casualties for the regiment cannot have been enormously heavy). Having fought at Lutterberg in 1758, it was distinguished at Bergen in 1759 and fought very well at Corbach in July 1760. It was also at Clostercamps in 1760, Langensalza in 1761 and Wilhelmstahl in 1762. (According to Susane, the grenadiers and chasseurs of this regiment distinguished themselves at the action of Neuhaus on the 13th September 1761.) At the end of the war Castellas became the garrison of Belfort.
[*Susane's volumes on the French infantry list officer casualties for all the Swiss regiments at Rossbach and it is interesting to compare them. I shall draw up a table when I have completed the flags for the Swiss units.]
Here are the flags for Castellas:
And this is the uniform and flag plate from the 1757 MS:
