According to the HTML5 standard, the default stroke and fill colors should be set to black (#000000). To stroke shapes, WebNode uses the fill color if no stroke color has been set, instead of the default black one.

http://www.html5canvastutorials.com/tutorials/html5-canvas-rectangles/
http://www.html5canvastutorials.com/tutorials/html5-canvas-circles/
http://www.html5canvastutorials.com/tutorials/html5-canvas-semicircles/
http://www.html5canvastutorials.com/advanced/html5-canvas-ovals/
http://www.html5canvastutorials.com/advanced/html5-canvas-linear-motion-animation/
http://www.html5canvastutorials.com/advanced/html5-canvas-quadratic-motion-animation/
http://www.html5canvastutorials.com/advanced/html5-canvas-oscillation-animation/
http://www.html5canvastutorials.com/advanced/html5-canvas-start-and-stop-an-animation/