Doing a text search for the button label, via the translation inputSpaceRulesUI_res.py file, I found this:
It looks like this "Reapply Rules to Scene" button is created in ...\Program Files\Autodesk\Maya2017\Python\Lib\site-packages\maya\app\colorMgt\inputSpaceRulesUI.py
in the function ChainRule.createUI, line 503
"Input Color Space" is the menu self._colorSpaceMenu created in ColorSpaceRule.createColorSpaceMenu in the same file, line 195.
Hopefully you can chase down what you need from there.