P10 Side Menu ThemeGrid_MarginGutter Background Color


I'm trying to change side menu background color. I want when clicked the menu area, some grey background color applies.

I use :active on css to apply the background color. But I cannot match the color. This is like something to do with ThemeGrid_MarginGutter properties.

Any help?

Please check the attachment to see how the colors cannot match.

This is another screenshot


All about css. Finally check on on active state on chrome dev tool and find brightness attributes defaulted to 0.7. This one makes active state always darker.