@alphachap, He is specifying the hexadecimal color notation, see Color.

@pjacobso, What exactly do you you mean?
If you just want to rotate it so that the boxes are slanted 45°, I did the following:

1. void setup() {
2.   size(500,500);
3.   smooth();
4.  }
5. void draw() {
6.  
7.  for (int s = 0; s < 640; s += 90) {
8.     for (int t = 0; t < 4800; t += 30) {
9.       pushMatrix();
10.       translate(width / 2, -height / 2);
11.       rotate(radians(45));
12.      
13.       fill(#0770FF);
14.      
15.       rect(s,t,10,10);
16.       rect(s+10,t+10,20,20);
17.      
18.       fill(#777FFF);
19.      
20.       rect(s+30,t,10,10);
21.       rect(s+40,t+10,20,20);
22.      
23.       fill(#07700F);
24.      
25.       rect(s+60,t,10,10);
26.       rect(s+70,t+10,20,20);
27.      
28.       popMatrix();
29.     }
30.   }
31. }
    

Basically rotated it 45° and translated it so that it appeared on the screen, not much else to it
(I also formatted you code so that it was slightly easier to read)
I hope this helped

OK; this isn't perfect (it doesn't fill the whole program) but:

1. void setup() {
2.   size(500,500);
3.   smooth();
4.  }
5. void draw() {
6.   translate(-width / 2, 0);
7.  
8.  for (int s = 0; s < 640; s += 90) {
9.     for (int t = 0; t < 4800; t += 30) {
10.       fill(#0770FF);
11.      
12.       rect(s+t,t,10,10);
13.       rect(s+t+10,t+10,20,20);
14.      
15.       fill(#777FFF);
16.      
17.       rect(s+t+30,t,10,10);
18.       rect(s+t+40,t+10,20,20);
19.      
20.       fill(#07700F);
21.      
22.       rect(s+t+60,t,10,10);
23.       rect(s+t+70,t+10,20,20);
24.     }
25.   }
26. }

Basically, I just added t to the x position of every rectangle, as well as the translation as to fit the most on the screen...
I hope this helped

OK: I just expanded the length of the for loop so that it fills the entire screen, it's not perfect though:

1. void setup() {
2.   size(500,500);
3.   smooth();
4.  }
5. void draw() {
6.   translate(-width, 0);
7.  
8.  for (int s = 0; s < 1000; s += 90) {
9.     for (int t = 0; t < 6000; t += 30) {
10.       fill(#0770FF);
11.      
12.       rect(s+t,t,10,10);
13.       rect(s+t+10,t+10,20,20);
14.      
15.       fill(#777FFF);
16.      
17.       rect(s+t+30,t,10,10);
18.       rect(s+t+40,t+10,20,20);
19.      
20.       fill(#07700F);
21.      
22.       rect(s+t+60,t,10,10);
23.       rect(s+t+70,t+10,20,20);
24.     }
25.   }
26. }

1. void setup() {
     size(1210,700);
     smooth();
     noLoop();
   }
2. void draw() {
   color[] colA;
   colA=new color[3];
   colA[0]=color(#0770FF);
   colA[1]=color(#777FFF);
   colA[2]=color(#07700F);
   int ci=2;
   for (int s = 0; s < 1180; s += 90) {
       for (int t = 0; t < 4800; t += 30) {
         fill(colA[ci]);
         rect(s,t,10,10);
         rect(s+10,t+10,20,20);
         fill(colA[(ci+1)%3]);
         rect(s+30,t,10,10);
         rect(s+40,t+10,20,20);
         fill(colA[(ci+2)%3]);
         rect(s+60,t,10,10);
         rect(s+70,t+10,20,20);
         ci=(ci+2)%3;
       }
         ci=(ci+1)%3;
     }
   }
3. void draw() {
   color[] colA;
   colA=new color[3];
   colA[0]=color(#0770FF);
   colA[1]=color(#777FFF);
   colA[2]=color(#07700F);
   int ci=2;
   for (int s = 0; s < 1180; s += 90) {
       for (int t = 0; t < 4800; t += 30) {
         fill(colA[ci]);
         rect(s,t,10,10);
         rect(s+10,t+10,20,20);
         fill(colA[(ci+1)%3]);
         rect(s+30,t,10,10);
         rect(s+40,t+10,20,20);
         fill(colA[(ci+2)%3]);
         rect(s+60,t,10,10);
         rect(s+70,t+10,20,20);
         ci=(ci+1)%3;
       }
     }
   }