Icons are nearly transparent

I created my first project with Ionic, and the icons are nearly transparent and hard to see. When I use Tabs, it only happens when the Tab is selected. The button to toggle the Menu is transparent all the time. Maybe I missed something during installing Ionic.

Does anybody have an idea how to fix the problem?Icons

Hi Paula @paulab and welcome to the community!

I think the first thing someone will ask you is to post the code that produces that issue (html and css).