The example you are referring to is programmed in an "object-oriented" manner, meaning the code for displaying a Spring object lives inside the Spring "class."  

Code:

class Spring {
 // all about a Spring
}
 

Since fill() uses a hard-coded value in the class, all Spring objects will always be colored with that same value, no matter how many Springs you make:

Code:

   void draw() 
  { 
    if(over) { 
	fill(153); 
    } else { 
	fill(255); 
    } 
    ellipse(tempxpos, tempypos, size, size);
  } 
 

If you want to make Springs each with a different color, you need to introduce a color variable inside the class.

Code:

class Spring 
{ 
   color normColor;
   color overColor;
   
  
  // Constructor
  Spring(float x, float y, int s, float d, float m, 
	   float k_in, Spring[] others, int id, 
	   color c1, color c2) 
  { 
     normColor = c1;
     overColor = c2;
  } 

  void draw() 
  { 
    if(over) { 
	fill(overColor); 
    } else { 
	fill(normColor); 
    } 
    ellipse(tempxpos, tempypos, size, size);
  } 
} 
 

Then you can make two Spring objects with different colors:

Code:

springs[0] = new Spring( 70, 160,  20, 0.98, 8.0, 0.1, springs, 0, color(255), color(150)); 
springs[1] = new Spring(150, 110,  60, 0.95, 9.0, 0.1, springs, 1), color(255,0,0), color(0,0,255)); 
 

For more about how objects and classes work in Processing, check out:

http://itp.nyu.edu/icm/shiffman/week3/index.html

works!