Turquoise (#40E0D0) is a light, moderately saturated cyan hue. Turquoise is a bright greenish blue named after the gemstone, evoking tropical water.
In RGB it is made of 64 red, 224 green and 208 blue. Its HSL hue angle is 174° with 72% saturation and 56% lightness, while its perceptual OKLCH lightness is 82% with a chroma of 0.131. For print, a starting CMYK mix is 71% cyan, 0% magenta, 7% yellow and 12% black.
As a text color on white, Turquoise has a contrast ratio of 1.64:1, which fails WCAG AA even for large text. On black it reaches 12.79:1 and passes AA for normal text. If you use Turquoise as a background, put black (or very dark) text on it. The APCA lightness contrast is Lc 76 for black text and Lc -32 for white text.
Its perceptual complement is #FFA8BC, close to pink. Colors that look most similar are seafoam, sky blue, aqua. People with red-green color blindness see turquoise quite differently (ΔE 13), so do not rely on it alone to signal meaning.