It's impossible to tell the type of rock based only on its color and location. Green-grey rocks are common in the Pacific Northwest, and the specific type can vary greatly depending on the geological formation and the minerals present.

Here are some possibilities for green-grey rocks in the Pacific Northwest:

* Basalt: A dark, fine-grained volcanic rock often found in the Columbia River Basalt Group. It can range in color from dark grey to greenish-grey, depending on the mineral content.

* Gabbro: A dark, coarse-grained igneous rock similar in composition to basalt but formed deep underground. It can also have a greenish-grey hue.

* Serpentinite: A metamorphic rock formed from ultramafic rocks like peridotite. It often has a greenish-grey color due to the presence of serpentine minerals.

* Slate: A fine-grained metamorphic rock formed from shale. It can be green-grey if it contains chlorite or other green minerals.

* Schist: A metamorphic rock with a foliated texture. It can have a green-grey color due to the presence of chlorite, mica, or other green minerals.

* Sandstone: A sedimentary rock formed from sand grains. It can be greenish-grey if it contains glauconite, a green mineral often found in marine environments.

To determine the specific type of rock, you would need to consider additional factors like:

* Texture: Is it fine-grained, coarse-grained, or foliated?

* Mineralogy: What specific minerals are present?

* Geological context: Where was the rock found? Is it part of a volcanic flow, a metamorphic belt, or a sedimentary formation?

It's best to consult a geologist or gemologist to accurately identify the rock. They can use various techniques like microscopy, chemical analysis, and field observations to provide a definitive answer.