Hover color change button right in the header.

Hello Andre,
Thank you so much for using our theme. Please check the color options on Customizer. If that is not helpful, please add the below css codes on Appearance > Customize > Additional CSS.

.top-header .read-more {
    background: yellow;
    border: orange;
}

Please change the color name or to color code as your required.
Hope this will help you.
Regards
Acme Supports

Most welcome.