Onyx Boox Poke5P User Manual page 15

Color
Add strokes to text
Some text may be invisible due to the background bleach.
Add strokes to text can make the text visible again.
Recommended value: 1.
Background Color
This is to bleach a large area of the background color. It is
recommended to use this setting together with text
enhancement and Icon Colors. Otherwise, the text and
small icons on the background will not be visible.
Icon Color
Generally, this is to darken the colors of some small colorful
icons in the menu.