RGB Signal Mast Controller

// RGB Signal Mast
const int RED = 3, YELLOW = 5, GREEN = 6;
const int BLOCK_AHEAD = 2;
const int BLOCK_NEXT = 4;

void setup() {
  pinMode(RED, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(BLOCK_AHEAD, INPUT_PULLUP);
  pinMode(BLOCK_NEXT, INPUT_PULLUP);
}

void setSignal(int r, int y, int g) {
  analogWrite(RED, r);
  analogWrite(YELLOW, y);
  analogWrite(GREEN, g);
}

void loop() {
  if (digitalRead(BLOCK_AHEAD) == LOW) {
    setSignal(255, 0, 0); // Red - block occupied
  } else if (digitalRead(BLOCK_NEXT) == LOW) {
    setSignal(0, 255, 0); // Yellow - approach
  } else {
    setSignal(0, 0, 255); // Green - clear
  }
  delay(100);
}