int [] numbers = new int[4];  
void setup(){
  size(400, 400);
  numbers[0] = 100;  
  numbers[1] = 100;  
  numbers[2] = 100;
  numbers[3] = 100;
  stroke(200);
}
void draw(){
  rect(numbers[0], numbers[1], numbers[2], numbers[3]);
} 
 

• Sometimes you have to set values in setup() instead of before it. Think of the preamble as getting out the different size containers you're going to need, and then in setup() you start putting stuff in to get it ready. Pretty much the same as how you set up classes and objects. Basic containers are all right to be pre-filled before setup() (int, float, String), but the more complex ones (arrays, objects) won't stand for it.
• color() returns an int value. It is used to make the assignment of colours easier to understand when you start working with Processing. eg:
  Code:

  
  color col = color(255,255,0);
  fill(col);
  rect(0,0,50,50);
  print(col);
   
  
  

  
  To my knowledge it doesn't initialise anything in the sketch. So color(52,32,0); on its own would be meaningless.