CODE CSS for begginers

RemNote Learning RemNote
#1

I want to create my theme, but since I don’t know the CSS language, I’m collecting data from other topics I find around here. Does anyone know the code to change the colors of the box that appears when selecting words? Even with a black theme, she’s still white. In case anyone knows of other codes, please post here. Thank you very much.

image

#2 
.rich-text-editor__selected-text-menu, 
.popup-menu, 
.mt-3,
.selectedResult,
.search-results,
#search-results__list,
#search-results__result
{
	background-color: black!important;
}

You can try this code…