Hi,

The CSS code is provided below: 

.ql-snow.ql-toolbar button:hover {
    color:  #9f1414 !important;
}
#wpdcom .ql-toolbar button:hover .ql-stroke{
    color: #9f1414 !important;
    stroke: #9f1414 !important;

}
#wpdcom .ql-toolbar button:hover .ql-fill:hover, #wpdcom .ql-toolbar button:hover .ql-fill {
    color: #9f1414  !important;
    fill: #9f1414  !important;
}

Please note: we don't provide CSS codes for style customization. 

Just find the classes by pressing F12 on the browser and opening Chrome or Firefox Console, it'll help you easily write CSS rules you need to customize.

Actually I had been trying for an hour how to change the color with Chrome's inspect.

I know you don't normally do this, but I couldn't make the change before. If that's not what I'm looking for, I'll come back to the forum.