Main Sketch

Marker shawn;
Marker fred;
Marker currentMarker;

void setup() {
  shawn = new Marker(color(0,255,0), 5, 100, "Flash");
  fred = new Marker(color(0,0,255), 70, 100000, "Cartoon");
  
  currentMarker = shawn;
}

void draw() {
  currentMarker.leak(mouseX,mouseY);
}

void mousePressed() {
  
  currentMarker.draw(mouseX,mouseY);  
}

void mouseDragged() {
 currentMarker.draw(mouseX,mouseY); 
}

void keyPressed() {
 if (key == '1') {
   // Shawn
   currentMarker = shawn;
 }
 else {
   // Fred
   currentMarker = fred;
 } 
}

Marker Class

class Marker {
 
 color myColor;
 int myRadius;
 int amountOfInk;
 String brand;
 
 
 public Marker(color _myColor, int _myRadius, int _amountOfInk, String _brand) {
   myColor = _myColor;
   myRadius = _myRadius;
   amountOfInk = _amountOfInk;
   brand = _brand;
 }
 
 void draw(int x, int y) {
   fill(myColor);
   if (amountOfInk > 0) {
     ellipse(x,y,myRadius,myRadius);
     amountOfInk--;
   }
 }
 
 void leak(int x, int y) {
   fill(myColor);
   if (amountOfInk > 0) {
     ellipse(x+int(random(-10,10)),y+int(random(-10,10)),random(0,myRadius),random(0,myRadius));
     amountOfInk--;
   }
 }
  
}