media.css

/* Extra Small Devices, .visible-xs-* */
@media (max-width: 767px) {
    h1 {
        font-size: 26px;
    }
}

/* Small Devices, .visible-sm-* */
@media (min-width: 768px) and (max-width: 991px) {
    h1 {
        font-size: 28px;color:red;
    }
}

/* Medium Devices, .visible-md-* */
@media (min-width: 992px) and (max-width: 1199px) {
    h1 {
        font-size: 30px;color:green;
    }
}

/* Large Devices, .visible-lg-* */
@media (min-width: 1200px) {
    h1 {
        font-size: 32px;color:blue;
    }
}