Implementation of rainbow style for multiple cells in a notebook

Question

We are aware that a user may utilize 'ColorFunction' gradients such as 'Rainbow' for plotting. How can we implement a gradient style as a rainbow spectrum to multiple cells in which there are multiple lines of commands, as shown in the image below?

I am aware of one method: using "Background Color" manually for each cell. However, if the number of cells is substantial, this procedure would be lengthy. How can this process be automatically implemented?

Answer 1

Is this what you are after?

colors = ColorData["Rainbow"] /@ Range[0, 1, .1];

With[{colors = colors, length = Length@colors},
 
 SetOptions[
  EvaluationNotebook[],
  StyleDefinitions -> Notebook[{
     Cell[StyleData[StyleDefinitions -> "Default.nb"]],
     Cell[StyleData["Input"],
      Background -> FEPrivate`Part[
        colors,
        FEPrivate`Mod[FrontEnd`CurrentValue[{"CounterValue", "Input"}], length, 1]
        ]
      ]
     }
    , StyleDefinitions -> "PrivateStylesheetFormatting.nb"
    ]
  ]
 
 
 
 ]