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2 
 int a = digitalRead(2);
Serial.println(a); //send value to serial

Sends the HIGH or LOW value as a string.

  if ( myPort.available() > 0) {  // If data is available,
    val = myPort.read();         // read it and store it in val
  }
  background(255);             // Set background to white
  if (val == 0) {              // If the serial value is 0,
    fill(0);                   // set fill to black
  }
  else {                       // If the serial value is not 0,
    fill(204);                 // set fill to light gray
  }

Expects a binary input, which was NOT what was received. Try

if(val == '0')