New to Bangle.js and Espruino. Need help with graphics

This might do the kind of thing you're after. By drawing just the poly (rather than using circles) you can avoid some flicker on the Bangle's unbuffered screen...

It's a good thing to try yourself though if you're interested - it's not that hard to use sin and cos and once you've got the hang of it it's really useful for a bunch of stuff

var n=0;

function drawSlice(from,to) {
  var a, res = 24;
  var x = 120, y = 120, r1 = 75, r2 = 95;
  var poly = [];
  for (var i=from*res;i<to*res;i++) {
    a = i*Math.PI*2/res;
    poly.push(x+r2*Math.sin(a), y+r2*Math.cos(a));
    poly.unshift(x+r1*Math.sin(a), y+r1*Math.cos(a));
  }
  a = to*Math.PI*2;
  poly.push(x+r2*Math.sin(a), y+r2*Math.cos(a));
  poly.unshift(x+r1*Math.sin(a), y+r1*Math.cos(a));

  g.fillPoly(poly);
}

function draw() {
  n += 0.01;
  if (n>=1) n=0;
  g.setColor(1,0,0);
  drawSlice(n,1);
  g.setColor(0,1,0);
  drawSlice(0,n);
}

setInterval(draw, 100);