How to change the color of ball everytime it strike the wall, in processing? My code is as below

Question

This is the code I have. And in next step how can I make effect on the bouncing ball from keyboard keys.

float circleX = 0;
float circleY = 0;

float xSpeed = 2.5;
float ySpeed = 2;

void setup() {
 size(500, 500); 
}

void draw() {
  background(0,200,0);

  circleX += xSpeed;
  if (circleX < 0 || circleX > width) {
    xSpeed *= -1;
  }

  circleY += ySpeed;
  if (circleY < 0 || circleY > height) {
    ySpeed *= -1;
  }

  ellipse(circleX, circleY, 100, 100);
}

Answer 1

Change the color fill() each time the ball hits a wall:

float circleX = 0;
float circleY = 0;
float xSpeed = 2.5;
float ySpeed = 2;

void setup() {
 size(500, 500); 
}

void changeColor() {
  fill(random(255), random(255), random(255));
}

void draw() {
  background(0,200,0);

  circleX += xSpeed;
  if (circleX < 0 || circleX > width) {
    xSpeed *= -1;
    changeColor();
  }

  circleY += ySpeed;
  if (circleY < 0 || circleY > height) {
    ySpeed *= -1;
    changeColor();
  }

  ellipse(circleX, circleY, 100, 100);
}