Turquoise family
#56B4BE
The fountain blue hex code is #56B4BE, part of the turquoise color family.
Lighter
#B2DCE1
Light
#82C7CE
Base
#56B4BE
Dark
#3C919A
Darker
#29646A
Close matches by hue, saturation, and lightness.
Colorframe lets you sample any pixel on your Mac and copy #56B4BE (or any color) in HEX, RGB, HSL, OKLCH, or CMYK.