The Silhouette rendering mode of Composer is a great way to present 3D models as if they were 2D drawings, which is beneficial for people who are in transition from 2D to 3D.
However, there are some limitations for this black and white rendering mode.
We often see our users struggling with some parts sticking to their original colors even in the Silhouette mode.
In such a case, the parts may have the Opacity values less than 255, and we can easily fix this issue by adjusting the Opacity value to be 255.
After the change, we can now see the desired rendering.
The other issue typically reported is that, when a cross-section plane is activated, the Silhouette mode suddenly turns to the Smooth rendering mode.
The solution is to change the Emission to be 1.000 and the color to be white for all parts: