The following is a list of Canvas rendering quirks for current and past browsers. It's possible to paint browser-specific content using these quirks.
For quirks with displayed color, a thin red stroke is used for the path (with a gray fill), and the following RGB color components indicate the content for the specified line-cap (many issues are only with one or a few types of line-caps):
Thus white areas will be included in all types of strokes, cyan will not be included in 'butt' line-cap strokes, etc.
When I have the available time, I'll be submitting bug reports for any remaining quirks (hopefully browsers will be consistent some day!)