This software is a homage to the old six colors Apple logo and to what that culture has meant for the community.
It draws a rainbow on the modeline according to the position of the point, so to have a horizontal scrollbar that shows you where the point is relatively to the size of the current buffer.
It's basically a fork of TeMPOraL Nyan-mode but without the cat, the animations and the music. The rainbow is based on the colors of the six colors rainbow logo that Apple used between 1977 and 1998.
Apple was 90 days away from going bankrupt back then. Was much worse than I thought when I went back. I actually asked people, ‘Why are you still here?’. And the answer was, ‘Because I bleed in 6 colors.’
-- Steve Jobs, on his return to Apple
And if you don't like the six-colors Apple logo, you can easily customizing the appearance by using the sixcolors-colors variable by using the standard M-x configure command under emacs or by manually set it to a list of colors (up to six obviously).
Some example, for italians users like me:
for the americans ones:
and if you are a nostalgic spectrum user:
This project is available on MELPA 
(use-package sixcolors-mode)
(sixcolors-mode)
If you want to customize the colors of your bar just set the single colors (up to six) as a list assigned to the sixcolors-colors variable.
For example:
(setq sixcolors-colors '("#009246" "#009246" "#FFFFFF" "#FFFFFF" "#CE2b37" "#CE2B37"))