ProCessing

size(256,256);

int i = 0;
int j = 0;
int g = 0;
int b = 0;

for(i=0;i<=16;i++){


  for(j=0;j<=16;j++){

    noStroke();
    fill(0,j*16,i*16);

    rect(16*j,16*i,16,16);


  }


}