- Create 3 new Surface Shaders.
- Assign one primary color to each shader and rename accordingly MatteRed, MatteGreen, and MatteBlue
- Create a new render layer, and name it something appropriate (RGBMatte_layer, for example)
- In that layer assign the Surface Shaders to a parts of the geometry that you wish to affect in 2D
- Render out a test frame of that layer to ensure that everything is working as expected
- In an After Effects file that has a “beauty” pass ready to receive 2D treatment, create an Adjustment Layer (Layer > New > Adjustment Layer) and ensure that it is sitting directly above the “beauty” pass in the timeline
- With the Adjustment layer selected, add a color correcting effect (Hue/Saturation, for example)
- Add the RGBMatte layer directly above the Adjustment Layer.
- With the RGBMatte layer selected, add a Set Matte effect to the RGBMatte layer (Effect > Channel > Set Matte)
- In the Set Matte effects controls
- Ensure that the Take Matte from Layer parameter is set to the RGBMatte layer
- Ensure that the Use for Matte parameter is set to the color channel that you wish to employ
- In the Timeline, under the TrkMat column, set the Adjustment Layer’s TrkMat to Alpha