Color mixing
Allow you to generate colors in between two picked colors.
Lock
If locked, you won't be able to add values out of the range, the sum of each color contribution will always be 100%.
Clamp vs Normalize
If the sum goes out of the range, clamp will simply set that parameter to 100%. By normalizing, a vector normalization will be applied on the value.
The two sliders represent how much each color contributes to the resulting colors, they're then simply mixed with RGB interpolation.