#define blueLED 5
#define redLED 3

void setup() {
  // put your setup code here, to run once:
  pinMode(blueLED, OUTPUT);
  pinMode(redLED, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  for (int r=0, b=255; r<=255, b>=0; r++,b--){
    analogWrite(blueLED, b);
    analogWrite(redLED, r);
    delay(20);
  }
}