Color

• Various ways to set a color:

// these all set the fillStyle to 'orange'
ctx.fillStyle = "orange";
ctx.fillStyle = "#FFA500";
ctx.fillStyle = "rgb(255,165,0)";
ctx.fillStyle = "rgba(255,165,0,1)";

• Use with fillStyle or strokeStyle

function drawcolors() {
  var ctx = document.getElementById('canvas').getContext('2d');
  for (i=0;i<6;i++){
    for (j=0;j<6;j++){
      ctx.fillStyle = 'rgb(' + Math.floor(255-42.5*i) + ',' + 
                       Math.floor(255-42.5*j) + ',0)';
      ctx.fillRect(j*25,i*25,25,25);
    }
  }
}
      

drawcolors()

function drawtransparency() {
  var ctx = document.getElementById('canvas2').getContext('2d');
  // draw background
  ctx.fillStyle = '#FD0';
  ctx.fillRect(0,0,75,75);
  ctx.fillStyle = '#6C0';
  ctx.fillRect(75,0,75,75);
  ctx.fillStyle = '#09F';
  ctx.fillRect(0,75,75,75);
  ctx.fillStyle = '#F30';
  ctx.fillRect(75,75,150,150);
  ctx.fillStyle = '#FFF';

  // set transparency value
  ctx.globalAlpha = 0.2;

  // Draw semi transparent circles
  for (i=0;i<7;i++){
      ctx.beginPath();
      ctx.arc(75,75,10+10*i,0,Math.PI*2,true);
      ctx.fill();
  }
}

drawtransparency()

function drawlineargradient() {
  var ctx = document.getElementById('canvas3').getContext('2d');

  // Create gradients
  var lingrad = ctx.createLinearGradient(0,0,0,150);
  lingrad.addColorStop(0, '#00ABEB');
  lingrad.addColorStop(0.5, '#fff');
  lingrad.addColorStop(0.5, '#26C000');
  lingrad.addColorStop(1, '#fff');

  var lingrad2 = ctx.createLinearGradient(0,50,0,95);
  lingrad2.addColorStop(0.5, '#000');
  lingrad2.addColorStop(1, 'rgba(0,0,0,0)');

  // assign gradients to fill and stroke styles
  ctx.fillStyle = lingrad;
  ctx.strokeStyle = lingrad2;
  
  // draw shapes
  ctx.fillRect(10,10,130,130);
  ctx.strokeRect(50,50,50,50);

}

drawlineargradient()

• createRadialGradient works similarly.