The timeline is shown in a wavy yellow line and there is a color code for each of the possible types of traveling:
> cyan for alien technology,
> green for forces of nature (read about wormholes and other exotica),
> red for time machines properly speaking,
> white for hibernations,
> and finally pink for any unknown origin.
The image appears in the book The Visual Miscellaneum by David McCandless (the aforementioned blog writer).