Strange color of model faces


Please help me how to fix this problem and what’s the cause?


You have inconsistent normals, some face normals point inwards and some outwards

Either turn on the face normal direction display in the properties and flip selected faces (W / flip normals) or select all faces and recalculate normals (Ctrl+N). If you have double vertices or non manifold edges you may have to do some further manual flipping.