General terms:
* Sage
* Olive
* Moss
* Khaki
* Forest green
* Pistachio
* Celadon
* Mint
* Aqua
More specific terms:
* Dusty green
* Greyish green
* Silver green
* Washed green
* Salvaged green
* Weathered green
* Seafoam
* Verdigris (a bluish-green patina that forms on copper)
Literary terms:
* Willow green
* Jade green
* Emerald green (though these are often more vibrant than muted)
The best word to use will depend on the context and the specific shade of green you are trying to describe.