Draw 3D model on top of another one

Question

I am trying to draw a 3D model I made with Blender in Monogame/XNA and this is the result I get when I draw 2 of them on top of each other

How can I make it so that the colors don't add up, but the one covers the other ? Here is my drawing code:

protected override void Draw(GameTime gameTime)
{
    GraphicsDevice.Clear(Color.Black);
    Vector3 modelPosition = new Vector3(-2500, 1500.0f, 0.0f);      
    Vector3 cameraPosition = new Vector3(0.0f, 0.0f, 5000.0f);
    float aspectRatio = (float)graphics.GraphicsDevice.Viewport.Width / 
          (float)graphics.GraphicsDevice.Viewport.Height;
    Vector3 scale = new Vector3(1f, 1, 1);
    Matrix[] transforms = new Matrix[Brick.Bones.Count];
    Brick.CopyAbsoluteBoneTransformsTo(transforms);
    foreach (ModelMesh mesh in Brick.Meshes)
    {
        foreach (BasicEffect effect in mesh.Effects)
        {
            effect.EnableDefaultLighting();
            effect.World = transforms[mesh.ParentBone.Index]*Matrix.CreateScale(scale)*
           Matrix.CreateRotationY(modelRotation)*Matrix.CreateTranslation(modelPosition);
            effect.View = Matrix.CreateLookAt(cameraPosition, Vector3.Zero, Vector3.Up);
            effect.Projection = Matrix.CreatePerspectiveFieldOfView(
                  MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f);
        }
        mesh.Draw();
    }           
    base.Draw(gameTime);
}

Answer 1

You need to set the blendstate to alpha blending when rendering your objects. You can do it like this:

GraphicsDevice.BlendState = BlendState.AlphaBlend;

This piece of code should go before drawing your mesh.