Choose your color scheme for the PDF Annotator user interface.
Just like for your operating system, you can choose between a Dark Mode and Light Mode for your PDF Annotator user interface. Select Extras Settings Display Application and select the preferred setting under Color Mode.
Keep in mind that your documents will not be affected by this setting. The PDF documents themselves will always get rendered exactly like a printer would print them.
If you are red-green colorblind, select Extras Settings Display Application and choose Accent Color: Blue to display the main tool icons in a blue color instead of red. Of course, you can always choose the color you prefer, even if you are not red-green colorblind.