This color wheel uses an SVG image to draw the color wells on the page. This allows us to use a wider variety of graphics: triangles, clipping paths, etc.
SVG does have the disadvantage that if it includes JavaScript, it must be inserted as part of an object element instead of an img element. Some browsers do not fully support the object element for SVG, especially resizing (this is you, Internet Explorer).
More color wheels:
CSS SVG HTML5 Canvas Itten Proportional