What pen can be used to paint the phone case black?

A black marker pen is enough and it won’t fade easily.

Mark pen, also called marker pen. Color pen A drawing and colored pen used for writing or drawing that contains ink and usually has a cap, usually a soft nib and a small and a large dual nib.

The paint of the marker pen is volatile and is used for quick drawing at one time. It is often used in artistic creation occasions such as design items, advertising slogans, and posters. You can draw a little variation and make the line thicker. A square pen is a marker pen. Markers are also divided into water-based and oil-based inks. Water-based inks are similar to colored pens and do not contain oil fragrance. Oil-based inks have a more pungent smell and are more volatile due to the oil fragrance. If the paint is peeling off, mark it with a marker.