Traffic lights

int GREEN = 2;
int YELLOW = 3;
int RED = 4;
int green = 5;
int red = 6;

void setup()
{
  pinMode(GREEN, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(RED, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(red, OUTPUT);
  }

void loop()
{
  green_light();
  delay(5000);
  yellow_light();
  delay(2000);
  red_light();
  delay(5000);
  green_light();
  delay(5000);
  red_light();
  delay(5000);
  }

void green_light()
{
  digitalWrite(GREEN, HIGH);
  digitalWrite(YELLOW, LOW);
  digitalWrite(RED, LOW);
  digitalWrite(green, LOW);
  digitalWrite(red, HIGH);
  }
void yellow_light()
{
  digitalWrite(GREEN, LOW);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(RED, LOW);
  }
void red_light()
{
  digitalWrite(GREEN, LOW);
  digitalWrite(YELLOW, LOW);
  digitalWrite(RED, HIGH);
  digitalWrite(green, HIGH);
  digitalWrite(red, LOW);
  }