Using the depth buffer in Color tranforms

Hi, I’m currently trying to code an outline post-processing effect to go with the built-in cel-shading – which by the way looks very nice. I’ve read in the documentation about custom color transforms and managed to implement basic ones. Is there a way to pass the depth buffer into a custom color transform, or any other piece of information from the graphic pipeline ? If not, should I plug my outline effect in Xenko.Rendering.Images.PostProcessingEffects, (and where if appropiate) ?
Thanks in advance.