Issue #3020418 by antoineh, ckrina, bnjmnm, fhaeberle, saschaeggi, andregp,...

Issue #3020418 by antoineh, ckrina, bnjmnm, fhaeberle, saschaeggi, andregp, ravi.shankar, priyanka.sahni, rkoller, huzooka, balsama, cindytwilliams, modulist, lauriii, antonellasevero: Update Placeholder styles so that contrast ratio passes guidelines