int Rpin= 3;
int Gpin= 5;
int Bpin= 6;
int trigpin= 8;
int echopin= A0;

void setup() {
  // put your setup code here, to run once:
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);
  pinMode(Rpin, OUTPUT);
  pinMode(Gpin, OUTPUT);
  pinMode(Bpin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(trigpin, LOW);
  digitalWrite(trigpin, HIGH);
  int value=pulseIn(echopin, HIGH);
  digitalWrite(Rpin, HIGH);
  digitalWrite(Gpin, LOW);
  digitalWrite(Bpin, LOW);
  delay(value);
  digitalWrite(Rpin, LOW);
  digitalWrite(Bpin, LOW);
  digitalWrite(Gpin, HIGH);
  delay(value);
  digitalWrite(Gpin, LOW);
  digitalWrite(Rpin, LOW);
  digitalWrite(Bpin, HIGH);
  delay(value);
}