This is the | lift_gamma_gain MLT frame work filter.
Allows you to adjust the lift (impacting mainly shadows), gain (impacting mainly highlights) and gamma (impacting mainly midtones). The color wheel inputs allow to control the degree to which these effects apply to the R, G & B color channels. By default, the white color at the centre of the colour wheel is selected, meaning the effect applies equally to all three color channels. By choosing another color on the color wheel, the effect will be applied on the R, G & B channels in proportion to the RGB components that make up that color.