The colors of 3D objects in Flux look dark and do not show colors correctly. For example, I took the Arduino-Nano-Every 3D model, in image number 1 you see have it looks like in Flux, and in image 4 you can see the same 3D model in Altium Designer.

1 - Flux

2 -Fusion 360

3 - SnapEDA

4 - Altium Designer