All I can say is that some people have way too much time on their hands - including me, apparently.
Although, it is kinda pretty - maybe I should embroider this on my shirt pocket . . .
● (blue): for links (the A tag)
● (red): for tables (TABLE, TR and TD tags)
● (green): for divisions (DIV tag)
● (violet): for images (IMG tag)
● (yellow): for forms (FORM, INPUT, TEXTAREA, SELECT and OPTION tags)
● (orange): for linebreaks and blockquotes (BR, P, and BLOCKQUOTE tags)
● (black): for root node ( HTML tag)
● (gray): all other tags