Similar shades:
* Greenish grey
* Dusty green
* Pale green
* Silver green
* Olive green
* Khaki
* Pistachio
* Willow
* Verdigris
More descriptive terms:
* Earthy
* Neutral
* Subdued
* Serene
* Calming
Other options:
* Salvia (the plant that gives the color its name)
* Sagebrush (the color of sagebrush plants)
Ultimately, the best alternative will depend on the specific shade of sage you're trying to describe.