在Qt中，如何改变滑块的背景颜色？

QSlider *slider = new QSlider(Qt::Horizontal);
slider->setRange(0, 100);
slider->setValue(50);

slider->setStyleSheet("QSlider::groove:horizontal {"
                      "background-color: #CCCCCC;"
                      "height: 10px;"
                      "border-radius: 5px;"
                      "}"
                      "QSlider::handle:horizontal {"
                      "background-color: #FF0000;"
                      "width: 20px;"
                      "border-radius: 10px;"
                      "margin: -5px 0;"
                      "}");

layout->addWidget(slider);