Colors are wrong in in-game screenshot

I'm making an in-game camera, but the colors in the final image are way off compared to the screen which it should be capturing. I'm not sure what setting is wrong. For testing purposes all post-processing effects are turned off.

  RenderTexture renderTex = cam.targetTexture;
             Texture2D renderResult = new Texture2D(picSize, picSize, TextureFormat.ARGB32, true);
             Rect rect = new Rect(0, 0, picSize, picSize);
             renderResult.ReadPixels(rect, 0, 0);
             renderResult.Apply();