#define LED_Red 2
#define LED_Yellow 4
#define LED_Green 7
int MY_PERIOD[] = { 300, 300, 300 };  // период в мс
uint32_t tmr, tmr1 = 0;
int i = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(LED_Red, OUTPUT);
  pinMode(LED_Yellow, OUTPUT);
  pinMode(LED_Green, OUTPUT);
}

void loop() {
  if (millis() - tmr >= MY_PERIOD[i]) {
    tmr = millis();
    switch (i) {
      case 0:
        digitalWrite(LED_Red, 1);
        break;
      case 1:
        digitalWrite(LED_Yellow, 1);
        break;
      case 2:
        digitalWrite(LED_Green, 1);
        break;
    }
    my_delay();
    digitalWrite(LED_Red, 0);
    digitalWrite(LED_Yellow, 0);
    digitalWrite(LED_Green, 0);
    i++;
    if (i > 2) i = 0;
  }
}

void my_delay() {
  tmr1 = millis();
  do {
  } while (millis() - tmr1 <= 500);
}