Yeah for that you will have to use the css class i provided.
create a theme.css or inject it in a styleclass
the easiest way is to inject it in a style class, the correct way is to make a theme.css
injection is done by putting the css in a styleclass background image surrounded by inverted brackets
}{ (no need to assign the class to anything)
a theme must be created here C:\Program Files\Inductive Automation\Ignition\data\modules\com.inductiveautomation.perspective\themes
and import your default theme file (light css) and set your default theme to the one you just made.
Do not edit existing themes as these will be lost on an update
make sure the id matches and you turn of resizing, and make it somewhat unique as it will work on all your projects and may sometimes cause unwanted behavior in other senarios