background: conic-gradient(red, orange, yellow, green, blue);

background: conic-gradient(from 0.25turn at 50% 30%, #f69d3c, 10deg, #3f87a6, 350deg, #ebf8e1);

background: conic-gradient(from 3.1416rad at 10% 50%, #e66465, #9198e5);

background: conic-gradient( 
     red 6deg, orange 6deg 18deg, yellow 18deg 45deg, 
     green 45deg 110deg, blue 110deg 200deg, purple 200deg);