Modify background color of bar-dark to two tones

Does anyone know how to set half and half background color of ionic bars.

I made this code in style.css, which works in the browser if I run “ionic serve”,
but it doesn’t work on the device after “ionic run android”. On the device the color is still the default #444.
Do I have to work with scss, if so could someone help because I don’t know how to do it with scss.

background: linear-gradient(to right, #000 0%, #000 50%, #ff6600 50%, #ff6600 100%) !important;