size(260,260);
background(192);

fill(0,0,255);
ellipse(260/2,260/2,250,250);

fill(0,255,0);
ellipse(260/2,260/2,200,200);

fill(255,0,255);
ellipse(260/2,260/2,150,150);

////

fill(0,255,255);
ellipse(260/2,260/2,100,100);

fill(255,255,0);
ellipse(260/2,260/2,50,50);

fill(255,0,0);
ellipse(260/2,260/2,25,25);