Microtek ScanMaker 6100 Pro User Manual page 91

Example: 0° corresponds to the color red on the Wheel, 60° to the
color yellow, 120° to the color green, 180° to the color cyan, 240°
to the color blue, and 300° to the color magenta.
Original After correction After correction
Radius
This field shows the amount of shift towards a particular color and
works in tandem with the Angle field. The Radius range extends
from 0 located at the center of the Color Wheel and indicating the
least concentration of color, to 1, located at the periphery of the
Wheel and indicating the greatest concentration of color.
Example: If your angle is 0° (red on the Color Wheel) and the radius
is 1, this results in an intense reddish cast on the entire image.
The Angle-Radius feature works differently from that of the
Saturation bar, which increases the saturation of all hues in the
image without tending towards any particular color cast.