How to change this icon + text color?

Thank you Adrien,

Please use the following CSS code, put it in Dashboard > Comments > Settings > Styling > "Custom CSS Code" textarea:

/* icon + text color */
#wpcomm .wpdiscuz-form-top-bar .wpdiscuz-user-settings{
    color: #3f00ff;
}
#wpcomm .wpdiscuz-form-top-bar #wc_show_hide_loggedin_username{
    color: #3f00ff;
}
#wpcomm .wpdiscuz-form-top-bar .wpdiscuz-user-settings:hover {
    color: #666;
}
/* background of comment number "1" beside "Poster un commentaire". */
#wc-comment-header .wpdiscuz-comment-count .wpd-cc-value{
    background: #3f00ff;
}
#wc-comment-header .wpdiscuz-comment-count .wpd-cc-arrow{
    border-top: 8px solid #3f00ff;
}

Don't forget to change the red marked color codes before using. 

Perfect!

Many thanks Astghik 🙂