alpha fade that weirdly works

int alpha = 10;
color[] colorArray  = {color(0,0,0,alpha),color(255, 192, 0,alpha),color(200, 0, 0,alpha),color(126, 255, 0,alpha)};
int currentColor;
int nextColor;

boolean change = false;

void setup(){
    size(640,480);
    smooth();
    noStroke();
    currentColor = 0;
}
void draw(){
    //background(colorArray[currentColor]);
    fill(colorArray[currentColor]);
    rect(0, 0, 1000, 1000);

    if(change){

        currentColor = nextColor;
        change = false;

    }
    //println("change: "+change);
}
void keyReleased(){
    if(key == 's'){
        change = true;
        println("currentColor: "+currentColor);
        int newColor = currentColor;
        while (newColor == currentColor)
        newColor=(int) random(colorArray.length);
        nextColor = newColor;
    }
}