I get this error:
Expecting DOT, found 'cols'

on this line:
  color[] cols = {

why, it's basicly the colorwheel example that get's delivered with processing.

1. int steps = 1;
   
   void setup() {
     size(800, 20);
   
     color[] cols = {
       color(255-(255/steps)*j, 255-(255/steps)*j, 0),  
       color(255-(255/steps)*j, (255/1.5)-((255/1.5)/steps)*j, 0),
       color(255-(255/steps)*j, (255/2)-((255/2)/steps)*j, 0),
       color(255-(255/steps)*j, (255/2.5)-((255/2.5)/steps)*j, 0),
       color(255-(255/steps)*j, 0, 0),
       color(255-(255/steps)*j, 0, (255/2)-((255/2)/steps)*j),
       color(255-(255/steps)*j, 0, 255-(255/steps)*j),
       color((255/2)-((255/2)/steps)*j, 0, 255-(255/steps)*j),
       color(0, 0, 255-(255/steps)*j),
       color(0, 255-(255/steps)*j, (255/2.5)-((255/2.5)/steps)*j),
       color(0, 255-(255/steps)*j, 0),
       color((255/2)-((255/2)/steps)*j, 255-(255/steps)*j, 0)
     }
   
     //for (int j = 0; j < steps; j++) {
     //println("255-(255/steps)*j, 255-(255/steps)*j, 0");
     //println("\t "+(255-(255/steps)*j)+"\t "+(255-(255/steps)*j)+"\t "+(0));
   }
   //}
   
   void draw() {
   
     for (int i = 0; i < cols.length; i++) {
       fill(cols[i]);
       rect(0, i*20, 20, 20);
     }
   }