Gray (#808080) is a medium, nearly neutral neutral. CSS gray is exactly 50% in sRGB, but perceptually it looks darker than a mid tone because sRGB is not linear.
In RGB it is made of 128 red, 128 green and 128 blue. Its HSL hue angle is 0° with 0% saturation and 50% lightness, while its perceptual OKLCH lightness is 60%. For print, a starting CMYK mix is 0% cyan, 0% magenta, 0% yellow and 50% black.
As a text color on white, Gray has a contrast ratio of 3.95:1, which passes AA only for large text and UI parts. On black it reaches 5.32:1 and passes AA for normal text. If you use Gray as a background, put black (or very dark) text on it. The APCA lightness contrast is Lc 37 for black text and Lc -72 for white text.
Its perceptual complement is #808080, close to gray. Colors that look most similar are slate gray, mocha, rose gold. It looks fairly similar to people with red-green color blindness (ΔE 0), so its meaning mostly survives.