How to send chars and values at the same time from processing to Arduino
The Arduino code sample you've provided is incomplete, and does not compile. On the Processing side, I would combine the LED On time with the Off time, using a separator, then ending with a \n. Something like this: myPort.write("1000:2000\n");.

There are many ways to parse the serial data into unsigned long to be used in the delay() function. Here is a sketch illustrating one way to parse it. I am using the serial monitor to send the following test data 1000:2000 (LED on for 1 second, off for 2 seconds). The serial monitor is sending the \n character.

char buffer[16];
unsigned long onTime;
unsigned long offTime;

void setup(){
  Serial.begin(9600);
  pinMode(13, OUTPUT);
}

void loop(){

  if(Serial.available() &gt; 0){

    Serial.readBytesUntil('\n', buffer, 13);

    char * pch;
    pch = strtok(buffer, ":");
    onTime = strtol(pch, &amp;pch, 10);
    pch = strtok(NULL, ":");
    offTime = strtol(pch, NULL, 10);

    digitalWrite(13, HIGH);
    delay(onTime);
    digitalWrite(13, LOW);
    delay(offTime);
    memset(buffer, 0, sizeof(buffer));
  }
}