gnome-control-center/panels/power/power.css

/* Battery levels */

levelbar block.warning-battery-offset {
  background-color: @error_color;
  border-color: @error_color;
}

levelbar block.low-battery-offset {
  background-color: @warning_color;
  border-color: @warning_color;
}

levelbar block.high-battery-offset {
  background-color: @success_color;
  border-color: @success_color;
}

/* Power profiles */

.power-profile.low-power {
  color: @success_color;
}

.power-profile.performance {
  color: @error_color;
}

.power-profile-info-row {
  padding: 6px 0;
}