how do i make it so that the similar colour tool gets changed into specific color tool?

I want to shade this one part but the problem is. Since my blockouts are all grey, everything in there is count as “similar colour” and i cant really select this one part without every other parts getting selected.

Any help on how to change that?

EDIT: i accidentally sent 2 pictures sorry

That is a difficult situation with all those similar shades of grey.
I don’t think the similar colour tool is the best one for that.

I suggest that you duplicate the layer and select the duplicate.
Then do Filter → Adjust → Levels and use that to get a good contrast between the region you want and the adjacent regions.
Then use the Contiguous Selection Tool with the Add action set in the Tool Optins docker so that you can ‘pick up’ any missing bits.

Before you do that, it may be a good idea to manually paint out (with white) the lower left adjacent rock face.

In the Tool Options just set the Fuzziness or however that numeric value is called in English to 1 (minimum value). Then it will select only pixels with the exact same color as the one on the pixel you clicked on. It will still pick up some pixels in the background because they have the same color, but you can easily remove the selection there using the Outline selection tool in the Subtract mode, for example.