How to add a black mask instead of white mask?

Thank you for the answer. Sorry I expressed wrong my question and in my photos it was not clear what type of "layer" , because my images show a sort of transparent or grey color layer. 
Moreover, it was not a layer what I was trying to change color, but it was a mask . 

I will edit my first question and adjust it, just in case someone need the same option.

I wanted to add a mask (not grey but black). But usually if one add a new mask is always white. To have a black mask, we have to click on 'new mask' button (in the levels panel) +  ALT. And the new mask will be black. 

ALT + click on add mask button, and the mask will be Black 😄

^^