The redish image from above was taken with the cover and LED ON. I already went through some crazy debugging path of the problem (including exchanging the GoPro ;)). I always use Protune and color grade my videos. I used many different white balance settings but prefer "native" to have the maximum control over the footage. I limit ISO to avoid noise in the footage but tried auto settings as well. Turning off the front LED resulted in much better footage but as stated in my first post in rare situations there is some light hue on dark surfaces. Aaaand here's the cover on my GoPro @ http://imgur.com/a/LHYy5.