the color is given by fill(red,green, blue).
you can for instance try: everytime you click, a random color is picked for shoes.

1. color c;
   void setup(){
   size(1025, 600);
   }
   void draw() {
   background(255);
   for (int x = 35; x < width +240; x += 240) {
       superhero(x, 110);
   }
   }
   
   void superhero(int x, int y) {
   int d = 80;
   int f = 15;
   //tried to do a loop for y but it wouldn't accept it
   
   
   //hair
   pushMatrix();
   translate(x, y);
   fill(102, 51, 0);
   rect(100, 100, 110, f);
   rect(80, 115, d, f);
   rect(80, 130, d, f);
   rect(55, 145, d, f);
   rect(55, 160, d, f);
   rect(55, 175, d, f);
   rect(55, 190, d, f);
   rect(100, 205, 60, f);
   rect(100, 220, 60, f);
   //face
   fill(255, 204, 153);
   rect(160, 115, 60, f);
   fill(255, 204, 153);
   rect(160, 130, 40, f);
   fill(255, 204, 153);
   rect(135, 145, 25, f);
   rect(135, 160, 25, f);
   rect(135, 175, 45, f);
   rect(135, 190, 65, f);
   fill(255, 204, 153);
   rect(225, 175, 35, f);
   rect(160, 190, 40, f);
   rect(160, 205, 70, f);
   rect(160, 220, 70, f);
   //hair
   fill(102, 51, 0);
   rect(200, 115, 35, f);
   fill(102, 51, 0);
   rect(200, 130, 35, f);
   //mask
   fill(102, 204, 0);
   rect(160, 145, 60, f);
   rect(160, 160, 90, f);
   rect(180, 175, 65, f);
   //mustache
   fill(153, 76, 0);
   rect(200, 190, 45, f);
   //suit
   fill(102, 204, 0);
   rect(80, 235, 120, f);
   rect(110, 250, 120, f);
   rect(110, 265, 100, f);
   rect(110, 280, 100, f);
   rect(110, 295, 100, f);
   rect(110, 310, 100, f);
   rect(140, 325, 40, f);
   //left arm
   fill(0);
   rect(60, 250, 50, f);
   rect(40, 265, 70, f);
   rect(40, 280, 50, f);
   //right arm
   rect(230, 250, 15, f);
   rect(210, 265, 55, f);
   rect(230, 280, 35, f);
   //legs
   fill(0);
   rect(90, 325, 50, f);
   rect(180, 325, 50, f);
   rect(70, 340, 50, f);
   rect(200, 340, 50, f);
   //shoes
   fill(c);
   rect(50, 355, 70, f);
   rect(200, 355, 70, f);
   //hands
   fill(192, 192, 192);
   rect(40, 295, 70, f);
   rect(40, 310, 50, f);
   rect(210, 295, 55, f);
   rect(225, 310, 40, f);
   popMatrix();
   }
   void mousePressed()
   {
     c = color(random(255),random(255),random(255));
   }

don't really understand what is your problem, because there's already color information in your code.

these are your shoes

1. //shoes
2. fill(102, 204, 0);
3. rect(50, 355, 70, f);
4. rect(200, 355, 70, f);

for a rect you can determine

• the outline color (with stroke()) or switch it off (with noStroke())
• or the fill color (with fill()) or switch off (with noFill()) - then you have an empty rect
  

you may find a cool color selector (in the menu tools iirc in the IDE) to choose colors and get the values e.g. for brown

for the line

1. fill(102, 204, 0);

1st value is red, 2nd green, 3rd blue:

• so max red is fill (255,0,0);
• so max green is fill (0,255,0);
• so max blue is fill (0,0,255);

Moved and changed thread title.

Take a look at: https://forum.processing.org/topic/where-to-place-threads-and-other-forum-practices