I just noticed today that my Opera GX has a color background behind it on the Taskbar how do I remove it and have it the default transparent no color

It would be nice if Opera GX had a Auto Hide Feature for the Sidebar I know there's a Keyboard Shortcut in flags that you can add but the thing is Opera the Default one has this Feature were the Sidebar will be hidden but if you move your mouse over to it, it will reappear.