Triadic
Backgrounds
Pick the HUE and saturation for the primary color.
And adjust the lightness for the primary color.
Variant
Set the saturation for the primary variant.
And the lightness for the primary variant.
Foregrounds
Pick the HUE and saturation for the secondary color.
Note that it determines the HUE for the tertiary color as well.
And the lightness for the secondary color.
Variant
Set the saturation for the secondary variant.
And the lightness for the secondary variant.
Accent
Select the saturation for the tertiary color.
And its lightness.