How can i change style on editor js when i use black theme(problems with hover)

Question

I'm seeking assistance with customizing the appearance of buttons in EditorJS when using a dark theme. Specifically, I'm trying to modify the plus button and another button represented by four dots. Presently, these buttons are styled appropriately when I use the white theme, appearing black with a grey hover effect, which looks good. However, upon switching to the dark theme, the buttons remain white upon hover, resulting in a dull appearance against the grey background. I would like to change the color of the buttons to black when hovered over, while keeping them white when not hovered. I've attempted to adjust the CSS to rectify this issue.

Below is the relevant CSS snippet:

.ce-toolbar__plus {
   color: white; 
}

Despite trying to change the hover color with the following:

.ce-toolbar__plus:hover {
    color: black;
    background-color: grey;
}

The color remains white, and !important doesn't seem to be effective. Any insights or suggestions on how to address this would be greatly appreciated. Thank you!