html {
  --s: 125px; /* control the size */
  --c1: #F8CA00;
  --c2: #BD1550;
  
  --_g: var(--c1) 90deg,var(--c2) 0 135deg,#0000 0;
  background:
    conic-gradient(from  -45deg at calc(100%/3)   calc(100%/3)  ,var(--c1) 90deg,#0000 0 ),
    conic-gradient(from -135deg at calc(100%/3)   calc(2*100%/3),var(--_g)),
    conic-gradient(from  135deg at calc(2*100%/3) calc(2*100%/3),var(--_g)),
    conic-gradient(from   45deg at calc(2*100%/3) calc(100%/3)  ,var(--_g),var(--c1) 0 225deg,var(--c2) 0);
  background-size: var(--s) var(--s);
}