Aquamarine (#7FFFD4) is a very light, highly saturated green hue. Aquamarine is a pale green-blue named after the gemstone, meaning sea water in Latin.
In RGB it is made of 127 red, 255 green and 212 blue. Its HSL hue angle is 160° with 100% saturation and 75% lightness, while its perceptual OKLCH lightness is 91% with a chroma of 0.130. For print, a starting CMYK mix is 50% cyan, 0% magenta, 17% yellow and 0% black.
As a text color on white, Aquamarine has a contrast ratio of 1.22:1, which fails WCAG AA even for large text. On black it reaches 17.16:1 and passes AA for normal text. If you use Aquamarine as a background, put black (or very dark) text on it. The APCA lightness contrast is Lc 93 for black text and Lc -13 for white text.
Its perceptual complement is #FFD5E8, close to millennial pink. Colors that look most similar are seafoam, electric blue, aqua. People with red-green color blindness see aquamarine quite differently (ΔE 13), so do not rely on it alone to signal meaning.