volatile char led_color_value = 0;

enum my_led_pins {
  COMMON_ANODE = 7,
  BLUE_CATHODE = 11,
  GREEN_CATHODE = 12,
  RED_CATHODE = 13,
};

void setup() {

  pinMode(RED_CATHODE, OUTPUT);
  pinMode(GREEN_CATHODE, OUTPUT);
  pinMode(BLUE_CATHODE, OUTPUT);
  pinMode(COMMON_ANODE, OUTPUT);

  digitalWrite(COMMON_ANODE, HIGH);
}

void loop() {

  led_color_value = (++led_color_value)%8;

  digitalWrite(RED_CATHODE, !(led_color_value & 0x1));
  digitalWrite(GREEN_CATHODE, !(led_color_value & 0x2));
  digitalWrite(BLUE_CATHODE, !(led_color_value & 0x4));

  delay(1000);
}