Why does the color output change? The png's are rendered well. The size, color, everything fits well. But when i convert the imagestrip into a MP4 file, the color output of the Video has changed. 
The black isnt black anymore its kinda red- and grey- toned. All colors are slightly brightened..

But why? While im watching Tutorials on Youtube theres no trouble at all with this... 

My feelin says its something about the colorpreferences on my system or in Blendersystem.. ?

Last week i changed the colors on my monitor.. i boost the black level and the saturation of colors. But i would never understand any connection to this mentioned problem.. precisely because the png's look perfect!

Does anyone know whats going on there?
(I tried a lot of codecs.. they do not change any colorvalues, also i tried RGB and BW in the rendersettings)
did you try to render a still image? If there is no problem with that I would suggest to always render animations just using still images, that has different advantages.

First, you can pause the render and continue at any point. 
Second there are just less possible problems, in my opinion. 
Third and most importantly, if something goes horribly wrong, for example your PC crashes, you do not have to start the render all over. 

The most preffered format for many is png, since it has a good balance between data size and quality loss, due to compression. 

Please comment, if this method is helpful, or not. :)