A colour cube is a representation of the colour gamut of a three-wavelength device (commonly red, green and blue). Each axis represents a different wavelength of additive colour, such that one corner is black, the three neighbouring vertices are red, green and blue, the three neigbouring them are yellow
(red+green), purple (red+blue) and turquoise (green+blue) and the opposite corner is white. Every point within the cube represents a different colour. The faces are similarly an array of colours.
Complicated? Please refer to the linked article - which includes a diagram.
With me now? Then I'll continue.
Suppose that one had an approximately cubic room one wished to tile. Perhaps a bathroom.
One could go to a tile shop and purchase one each of a great many colours of tile, representing the colours on each face of the cube. They're often neatly arrayed by colour, as if this is what they want you to do.
Then very carefully tile your room.
It almost goes without saying that one should carefully extend the motif to any inset walls, using colours at the appropriate place within the cube.
Further improvements involve the incorporation of chromatically appropriate stained glass and LED lighting.