There are more faces involved than the ones mentioned in the link you pointed to. The answer is to use
C-u C-x = to find out what faces are involved. Those are the ones you need to customize.
M-x customize-face to customize the faces you are interested in. If you don't know which faces they are, put the cursor on that highlighted text and use
C-u C-x =. Look near the bottom of
*Help* for the face name.
From @djangoliv's answer it seems that these are the faces you need to customize:
M-x customize-face diff-refine-added and define the face as you like.
Do the same for
Easy, persistent, and the way Emacs wants to help you customize faces. See the Emacs manual, node Specific Customization.