ho creato un codice preso all'interno del file
custom_backforward_large.css di Aris per ottenere i tasti avanti e indietro in grigio solido quando si lancia il browser con una sola pagina aperta come accadeva in firefox 56.0.2 e waterfox classic, me lo appare in stile lucido o sfumatura che in inglese è glossy e shade, non riesco a rimuovere la sfumatura/lucido.
WATERFOX CLASSIC

WATERFOX

ho impostato la scala grigio e il contrasto
/* TASTI AVANTI E INDIETRO COLORE (custom_backforward_large.css) */
#main-window:not([uidensity=compact]):not([uidensity=touch]) #navigator-toolbox #nav-bar #back-button .toolbarbutton-icon,
#main-window[uidensity=compact] #navigator-toolbox #nav-bar #back-button .toolbarbutton-icon,
#main-window[uidensity=touch] #navigator-toolbox #nav-bar #back-button .toolbarbutton-icon,
#main-window #navigator-toolbox #nav-bar #back-button .toolbarbutton-icon {
width: 36px !important;
height: 32px !important;
}
#main-window:not([uidensity=compact]):not([uidensity=touch]) #navigator-toolbox #nav-bar #forward-button .toolbarbutton-icon,
#main-window[uidensity=compact] #navigator-toolbox #nav-bar #forward-button .toolbarbutton-icon,
#main-window[uidensity=touch] #navigator-toolbox #nav-bar #forward-button .toolbarbutton-icon,
#main-window #navigator-toolbox #nav-bar #forward-button .toolbarbutton-icon {
width: 30px !important;
height: 32px !important;
}
#main-window[uidensity=compact] #nav-bar #nav-bar-customization-target > :is(#back-button, #forward-button) {
margin: unset !important;
padding: unset !important;
}
#main-window:not([uidensity=compact]):not([uidensity=touch]) #nav-bar #nav-bar-customization-target > #forward-button,
#main-window[uidensity=touch] #nav-bar #nav-bar-customization-target > #forward-button {
margin-inline-start: -2px !important;
}
#main-window #navigator-toolbox #nav-bar :is(#back-button, #forward-button):not([disabled]):hover .toolbarbutton-icon {
filter: brightness(1.3) !important;
}
#main-window #navigator-toolbox #nav-bar :is(#back-button, #forward-button):not([disabled]):is(:active,:hover:active,[open]) .toolbarbutton-icon {
filter: brightness(0.9) contrast(175%) !important;
box-shadow: 0px -1px 0 1px rgba(0,0,0,0.3) !important;
}
#main-window #navigator-toolbox #nav-bar :is(#back-button, #forward-button)[disabled] .toolbarbutton-icon {
opacity: 1.0 !important;
filter: grayscale(100%) contrast(210%) !important;
}
#main-window #navigator-toolbox #nav-bar :is(#back-button, #forward-button)[disabled] {
opacity: 1.0 !important;
}
#main-window:not([uidensity=compact]):not([uidensity=touch]) #nav-bar #nav-bar-customization-target > #forward-button,
#main-window[uidensity=touch] #nav-bar #nav-bar-customization-target > #forward-button {
margin-inline-start: -4px !important;
}