It's not a real issue but you have defined background-color for ".button-group.minor-group .button:active" twice.
.button-group.minor-group .button:hover,
.button-group.minor-group .button:focus,
.button-group.minor-group .button:active {
background-color: #599bdc;
}
.button-group.minor-group .button:active,
.button-group.minor-group .button.active {
background-color: #3072b3;
}
.button-group.minor-group .button:hover,
.button-group.minor-group .button:focus {
background-color: #599bdc;
}
.button-group.minor-group .button:active,
.button-group.minor-group .button.active {
background-color: #3072b3;
}