Fastext is a 'relatively new' service which allows the user to navigate the pages of a teletext system quicker than if they were to directly input the page number.
Four coloured links at the foot of the page correspond to four similarly coloured buttons on the remote control handset. Each link leads to a page related to the current one. This colour coding is by no means original - arcade video games often used it to distinguish between buttons on the control panel. In the 90s, the Super Nintendo home console also came packaged in the PAL region with the joypad shown below:
It would seem this combination of the three primary colours and green is a popular colour coding for button interfaces. This aspect of colouring has largely been lost in the web - designers prefer to choose neutral colours, with more vivid hues being used sparingly. Links tend to be a uniform colour to distinguish them from the rest of the page's text, defaulting to navy blue. Body text is invariably dark on a light background though is occasionally light on dark, as in this weblog.