RasterColorMix

When raster-color is active, specifies the combination of source RGB channels used to compute the raster value. Computed using the equation mix.r * src.r + mix.g * src.g + mix.b * src.b + mix.a. The first three components specify the mix of source red, green, and blue channels, respectively. The fourth component serves as a constant offset and is not multipled by source alpha. Source alpha is instead carried through and applied as opacity to the colorized result. Default value corresponds to RGB luminosity.