Two men wonder why colour always eventually fades away from everything. When flowers wither and die they lose their colour, the colour in coloured paper left outside will eventually drain out, even coloured plastic will, after a long long time, have its colour seep away.
They eventually discover a parallel world to their own; this parallel world sucks out and steals the colour from their world and utilises it as their energy source. The two men then decide to introduce the concept of using colour as an energy source in their world.
Eventually, the world consumes too much of its colour as an energy source and starts to run out of colour. Future generations start to consider the sighting of something with colour a rare sight.