The ramp color dominates the Voronoi [position] as we have witnessed.
Design or Defect? Why? Perhaps the Blender Foundation can be asked.
The Blender Render texture settings can desaturate the position Voronoi colors to gray.
Once a gray is achieved the Blender Render can change colors based on a mapping space such as UV with a ramp.
The texture settings ramp can NOT change a color randomly based on a previous color, that information is not present. That is a feature of the node systems.
The visual similarity of the color ramp in the Cycles Material Nodes and the Blender internal material/texture ramp is deceiving. The Cycles node color ramp produces a color based on an input. The Blender internal Material/Node color ramp specifies a color in a texture coordinate space which can be used to blend.
[ I want something like if I put a cells Voronoi texture through a color ramp in the cycles node editor]. The texture settings of the material/texture without nodes cannot do this.
Perhaps we are using Cycles nodes so much we forget the old lesser capabilities of Blender Internal Material Textures.
It appears we are looking for a feature in the wrong place.
The node system of Blender Render can recolor a Voronoi texture based purely on color.
The node system of Cycles Render can recolor a Voronoi texture based purely on color.
Of course stating the some feature is not present in some area of Blender is a dangerous act.