They're colors like brown dark orange and such. Colors that you might find in a forest ie the color of trees, dirt, etc. Earthy colors are darker than others
No it is not, it's not proper grammar
Earthy: 1 a: of, relating to, or consisting of earth b: suggestive of earth (as in texture, odor, or color) c: rough, coarse, or plain in taste 2 aarchaic :...