There are four colour models you can use.
In the HLS Keyer menu, you set the softness and tolerance ranges using the hue, luminance, and saturation channels.
In the YUV Keyer menu, you set the softness and tolerance ranges using the luma and chroma signals of YUV component video.
In the RGB Keyer menu, you set the softness and tolerance ranges using the red, green, and blue channels.
In the RGBCMYL Keyer menu, you set the softness and tolerance ranges using the red, green, blue, cyan, magenta, yellow, and luminance channels. This colour model provides subpixel resolution.