Define selected class.

Update:

Ok I figured out that I can make them all unselect by default by changing src/selector_manager/model/Selector.js

   active: false,

and this pretty much solves all my problems as when I change the background color of the block, it will update only c875!.

Closing this as it's now solved.

You can access selectors from the model

model.get('classes').each(selector => selector.set('active', 0))

or for example, disable them all from its module

editor.SelectorManager.getAll().each(selector => selector.set('active', 0))

fyi changing this to false will make your build to fail due to this in the test script:

I just commented this out here: test/specs/selector_manager/model/SelectorModels.js

        // it('Has active property', () => {
        //   expect(obj.has('active')).toEqual(false);
        // });

and this

test/specs/css_composer/e2e/CssComposer.js line 129

 ruleOut = JSON.parse(JSON.stringify(ruleOut));
          var ruleResult = {
            mediaText: '',
            selectors: [{
             active: false, //changed this to false