citra/dist/qt_themes/default/style.qss

QPushButton#TogglableStatusBarButton {
    color: #959595;
    border: 1px solid transparent;
    background-color: transparent;
    padding: 0px 3px 0px 3px;
    text-align: center;
}

QPushButton#TogglableStatusBarButton:checked {
    color: #000000;
}

QPushButton#TogglableStatusBarButton:hover {
    border: 1px solid #76797C;
}

QPushButton#RendererStatusBarButton {
    color: #656565;
    border: 1px solid transparent;
    background-color: transparent;
    padding: 0px 3px 0px 3px;
    text-align: center;
}

QPushButton#RendererStatusBarButton:hover {
    border: 1px solid #76797C;
}

QPushButton#RendererStatusBarButton:checked {
    color: #e85c00;
}

QPushButton#RendererStatusBarButton:!checked {
    color: #0066ff;
}

QPushButton#buttonRefreshDevices {
    min-width: 20px;
    min-height: 20px;
    max-width: 20px;
    max-height: 20px;
}

QCheckBox#checkboxPlayer1Connected,
QCheckBox#checkboxPlayer2Connected,
QCheckBox#checkboxPlayer3Connected,
QCheckBox#checkboxPlayer4Connected,
QCheckBox#checkboxPlayer5Connected,
QCheckBox#checkboxPlayer6Connected,
QCheckBox#checkboxPlayer7Connected,
QCheckBox#checkboxPlayer8Connected {
    spacing: 0px;
}

QCheckBox#checkboxPlayer1Connected::indicator,
QCheckBox#checkboxPlayer2Connected::indicator,
QCheckBox#checkboxPlayer3Connected::indicator,
QCheckBox#checkboxPlayer4Connected::indicator,
QCheckBox#checkboxPlayer5Connected::indicator,
QCheckBox#checkboxPlayer6Connected::indicator,
QCheckBox#checkboxPlayer7Connected::indicator,
QCheckBox#checkboxPlayer8Connected::indicator {
    width: 14px;
    height: 14px;
}

QCheckBox#checkboxPlayer1Connected::indicator:checked,
QCheckBox#checkboxPlayer2Connected::indicator:checked,
QCheckBox#checkboxPlayer3Connected::indicator:checked,
QCheckBox#checkboxPlayer4Connected::indicator:checked,
QCheckBox#checkboxPlayer5Connected::indicator:checked,
QCheckBox#checkboxPlayer6Connected::indicator:checked,
QCheckBox#checkboxPlayer7Connected::indicator:checked,
QCheckBox#checkboxPlayer8Connected::indicator:checked,
QGroupBox#groupConnectedController::indicator:checked {
    border-radius: 2px;
    border: 1px solid black;
    background: #39ff14;
    image: none;
}

QCheckBox#checkboxPlayer1Connected::indicator:unchecked,
QCheckBox#checkboxPlayer2Connected::indicator:unchecked,
QCheckBox#checkboxPlayer3Connected::indicator:unchecked,
QCheckBox#checkboxPlayer4Connected::indicator:unchecked,
QCheckBox#checkboxPlayer5Connected::indicator:unchecked,
QCheckBox#checkboxPlayer6Connected::indicator:unchecked,
QCheckBox#checkboxPlayer7Connected::indicator:unchecked,
QCheckBox#checkboxPlayer8Connected::indicator:unchecked,
QGroupBox#groupConnectedController::indicator:unchecked {
    border-radius: 2px;
    border: 1px solid black;
    background: transparent;
    image: none;
}