Individual colors for a series of shapes

Hi everyone ! So I thought my problem was solved once we got over this question of colored rectangles. ( https://forum.processing.org/two/discussion/comment/109296#Comment_109296 )

But not at all. This time I don't want random colors, and making an array isn't enough... So my question is the same as before: how to draw each rectangle so that its color stays the same, independently from the following rectangles? I want the color to change according to the frequency. Here is the code:

import ddf.minim.*;
import ddf.minim.analysis.*;

Minim minim;
AudioPlayer song;
FFT fft;
float highestAmp = 0;
int frequency;
float amplitude;
int rectX;
float time;
color[] colors = new color[3];

void setup(){
  size(1500,500);
  background(255);


    // initialize Minim and catching the output
  minim = new Minim(this);
  song = minim.loadFile("altj.mp3",1024);
//better result with *8
fft = new FFT(song.left.size(), 44100);
song.play();

// define 3 colors
colors[0] = color(255,0,0);
colors[1] = color(255,255,0);
colors[2] = color(0,255,0);
 }


 void draw (){
   highestAmp=0;
   amplitude=0;
   frequency=0;
   fft.forward(song.left);
   background(255);

   // get frequency from 0Hz to 20000Hz
   for(int i = 0; i < 20000; i++){
     amplitude = fft.getFreq(i);
     if (amplitude > highestAmp) {
       highestAmp = amplitude;
       frequency = i;
     }
   }
   //make it move !
   for (int x = 0; x < time; x = x+5) {
     // color frequencies
    if (frequency < 70){
    fill(colors[0]);
    }else if (frequency < 250){
      fill(colors[1]);
    }else{
    fill(colors[2]);
    }
    rect(x,0,5, height);
  }
time++;
 }

I learned about classes and tried to use them (still a noob, haha). It looks like this :

Slot mySlot;
float x;
color[] colors = new color[3];
import ddf.minim.*;
import ddf.minim.analysis.*;

Minim minim;
AudioPlayer song;
FFT fft;
float highestAmp = 0;
int frequency;
float amplitude;

void setup()  {
  size(1500,500);
  // initialize Minim and catching the output
  minim = new Minim(this);
  song = minim.loadFile("altj.mp3",1024);
//better result with *8
fft = new FFT(song.left.size(), 44100);
song.play();

  mySlot = new Slot ();
  colors[0] = color(255,0,0);
  colors[1] = color(255,255,0);
  colors[2] = color(0,255,0);
}

void draw()  {
  highestAmp=0;
   amplitude=0;
   frequency=0;
   fft.forward(song.left);

   // get frequency from 0Hz to 20000Hz
   for(int i = 0; i < 20000; i++){
     amplitude = fft.getFreq(i);
     if (amplitude > highestAmp) {
       highestAmp = amplitude;
       frequency = i;
     }
   }

  mySlot.display();
  mySlot.avance();
  x = 0;
  if (frequency <70){
    fill(colors[0]);
    }else if (frequency < 250){
      fill(colors[1]);
    }else{
      fill(colors[2]);
    }
    rect(x,0,5, height);

}

class Slot{

  //Data
  float x;
  float time;

  //Constructor
  Slot(){
    x = 0;
  }

  //Functionality
  void display() {
    rect(x,0,5,height);
  }

  void avance(){
    x = 0;
    for(int x = 0; x < time; x = x + 5){
      rect(x,0,5,height);
    }
    time++;
    if (x > width) {
      x = 0;
    }
  }
}

But same problem: the "fill" color is inside the same draw function as the rectangle. I don't know how I can separate it from the above line of the shape, or make a series of shapes related to these conditions for colors... Any clue?