In this image I have to change red to grey:

I know I can just set the saturation to zero, but then the result is a grey that is to dark.

I could just change the brightness, but that would also change the left lower part of the picture:

Is there an adjustment that only works on the red parts of the image? I can't use a selection, because the setting has to be applied to lots of images.

EDIT

I tried to use "replace adjustment tool", but that did not work well for the shdows and bright parts of the image, even with the largest fuzzines. I used blue as the replacement colour, to have a better impression of what it does.