As a Roblox developer, it is currently not possible to not have the sun reflect on parts. Sun reflections on SmoothPlastic are especially obnoxious in some cases, and there is no way to remove it. In most games, sun reflections make the game look better. However, there are some cases where we don’t want that.
In the game I am currently working on, I am trying to use the SmoothPlastic material for solid colors. At certain angles, the sun reflects on it and makes it look much brighter. I would like for it to appear the same color at all angles.
Those aren’t called reflection from my own 3D modeling experience. According to Blender, they are actually called specular. The API on the Lighting only allows it to be amplified and not actually removing the specular completely: