int redPin = 12;
int greenPin = 11;
int bluePin = 10;
char myColor[20];
char buff[20];
char msg[]={"What color LED? "};
byte recvCount = 0;
bool haveColor= false;
unsigned long lastBlink;
int intervalBlink = 250;

void setup() {
  // put your setup code here, to run once:

  Serial.begin(9600);
  Serial.println("Ready");

  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);

digitalWrite(redPin, HIGH);
digitalWrite(greenPin, HIGH);
digitalWrite(bluePin, HIGH);
delay(2000);
digitalWrite(redPin, LOW);
digitalWrite(greenPin, LOW);
digitalWrite(bluePin, LOW);

  Serial.println(msg);

}

void loop() {
  // put your main code here, to run repeatedly:

if (Serial.available()){
  byte abyte = Serial.read();
  if (abyte != 10){
    buff[recvCount]=abyte;
    recvCount++;
    if (recvCount>=sizeof(buff)) recvCount = 0;//??no!!
  }else {
    memcpy(myColor,buff,sizeof(buff));
    haveColor = true;//set flag
    recvCount = 0;
    memset(buff,0,sizeof(myColor));//empty buff
    Serial.println(msg);
  }
}

  if (strcmp(myColor, "red")==0 || strcmp(myColor, "Red")==0) {
  if (millis()-lastBlink>=intervalBlink){
    lastBlink = millis();
    digitalWrite(redPin, !digitalRead(redPin));
    digitalWrite(greenPin, LOW);
    digitalWrite(bluePin, LOW);
  }  
  }

  if (strcmp(myColor, "green")==0 || strcmp(myColor, "Green")==0) {
  if (millis()-lastBlink>=intervalBlink){
    lastBlink = millis();
    digitalWrite(greenPin, !digitalRead(greenPin));
    digitalWrite(redPin, LOW);
    digitalWrite(bluePin, LOW);
  }  
  }

  if (strcmp(myColor, "blue")==0 || strcmp(myColor, "Blue")==0) {
  if (millis()-lastBlink>=intervalBlink){
    lastBlink = millis();
    digitalWrite(bluePin, !digitalRead(bluePin));
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, LOW);
  }  
  }

  if (strcmp(myColor, "stop")==0 || strcmp(myColor, "Stop")==0) {
    digitalWrite(bluePin,LOW);
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, LOW);
  }

  
 }