spec

7.1. Angle Units: the type and deg, grad, rad, turn units

Angle values are s denoted by . The angle unit identifiers are:

deg
Degrees. There are 360 degrees in a full circle.

grad
Gradians, also known as "gons" or "grades". There are 400 gradians in a full circle.

rad
Radians. There are 2π radians in a full circle.

turn
Turns. There is 1 turn in a full circle.

Aiming to get the color indicator here :

color: hsl(0.5turn 100% 50%);
color: hsl(200grad 100% 50%);
color: hsl(3.14159rad 100% 50%);