I believe that because the outline pass is additive, it really only matches the given color well for fully-saturated colors. E.g. RGB = 1, 1, 0 will work, but RGB = 1, 1, 0.5 may not. Perhaps that could be changed/fixed, I’m not sure.
I tested all blendFunctions. 0-18 won’t give me the correct result and >19 lead to an error.
Do you have any idea what’s the problem with 1.? Even without Outline the background color changes if I enable the EffectComposer: Outlines (forked) - CodeSandbox
I’m not aware of any way to set an exact color for the outline. The effect may need to be customized, or you could file an issue or feature request on the post processing module.
For the background color — Any use of post processing will change how and where color management works, and works differently in three.js post processing VS. the separate pmndrs/postprocessing project. I think the quick fix would be to do convertSRGBToLinear() on your background color when using it with post processing.
Could you please let me know how to get correct colors. I tried all blending options. I am on 0.157.0. But the outline color always differs from the color I state to the props. In addition to that the outline color is different if either another object or the background is behind the line.