Slate Gray (#708090) is a medium, muted blue hue. Slate gray has a cool blue undertone, named after the rock.
In RGB it is made of 112 red, 128 green and 144 blue. Its HSL hue angle is 210° with 13% saturation and 50% lightness, while its perceptual OKLCH lightness is 59% with a chroma of 0.031. For print, a starting CMYK mix is 22% cyan, 11% magenta, 0% yellow and 44% black.
As a text color on white, Slate Gray has a contrast ratio of 4.05:1, which passes AA only for large text and UI parts. On black it reaches 5.18:1 and passes AA for normal text. If you use Slate Gray as a background, put black (or very dark) text on it. The APCA lightness contrast is Lc 36 for black text and Lc -73 for white text.
Its perceptual complement is #8B7B6B, close to mocha. Colors that look most similar are gray, steel blue, mocha. It looks fairly similar to people with red-green color blindness (ΔE 1), so its meaning mostly survives.