I am doing a rendering with a transparent cover and parts inside. I am using no light and just illumination with romm walls set to constant. Doing that, my blue parts inside render as grey with no color. I have shadows and I can see the shape but it is just in gray scale. If I remove the transparent part, insides parts appears in blue as they should be.
I discovered that if I add some lights the color just appear now as it should be in real life. Is it a bug or something I just did not understand something?