Círculos en Processing

Ellipse 

size (400,400);

background (0,0,0);

fill (250,0,50);

ellipse (200,200,400,400);

fill (137,255,18);

ellipse (200,200,350,350);

fill (255,98,0);

ellipse (200,200,300,300);

fill (72,255,207);

ellipse (200,200,250,250);

fill (250,0,50);

ellipse (200,200,200,200);

fill (137,255,18);

ellipse (200,200,150,150);

fill (255,98,0);

ellipse (200,200,100,100);

fill (72,255,207);

ellipse (200,200,50,50);