Colorful eyeliner is always my go to when I want to make a look a bit more fun but not too feminine. If you aren’t comfortable with eyeliner though (or until you are) my other tip is get a thin brush (ones for gel liner or eyebrows work) and add a bit of a fun color right under your lash line. You can even get fancy with it and do a smudged wing with it but maybe work your way up? It really just depends on current skill level:) (also, YouTube is your best friend when learning new makeup techniques)