Hi Christian,
I think you are executing this Simulink model in normal mode (and thus not getting a connection to the RPi). So you get the moving colorbars mentioned in the first paragraph here: http://www.mathworks.com/help/supportpkg/raspberrypi/ref/v4l2videocapture.html
I recommend if you want to get the Simulink support running, first do these two shipping examples: http://www.mathworks.com/help/supportpkg/raspberrypi/examples/getting-started-with-raspberry-pi-hardware.html http://www.mathworks.com/help/supportpkg/raspberrypi/examples/image-inversion.html
You'll see it in action.
Note that the Simulink Target - actually programs the board - and runs on the board. So when you hit play in Simulink normal mode - you didn't initiate that workflow (and just get the color bars). that is a means to test prior to running on board. Although with External Mode - you also can monitor execution in Simulink - you can see that in either of the examples below.
Separately - it isn't clear which workflow you actually want/prefer. you may want Simulink to run in simulation mode and get Rpi inputs/outputs while MATLAB/Simulink is running (similar to the MATLAB Support Package for RPi). That is not included in either support package.
you can see both solutions described here: http://www.mathworks.com/hardware-support/?q=vendor:%22Raspberry+Pi%22
It would be helpful for us to understand if you do want to have the ability to perform input/output device from Simulink with Rpi (as you do with MATLAB) - without programming algorithms on board. If you can help us understand your usecase for this feature - we can consider future improvements.
HTH Dan
