This might get you started - select a paragraph and run the macro to remove the shading from paragraphs with that same colour.
Note: Your results might vary according to how the colours are applied. In my quick testing the macro was greedy and removed colours from other paragraphs that were coloured from the same row of the colour palette (ie same tint level). It worked fine if the colours came from other levels of tint or were defined in RGB.
Code:
Sub Macro2()
Dim iCol As Long
iCol = Selection.Shading.BackgroundPatternColor
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = ""
.ParagraphFormat.Shading.BackgroundPatternColor = iCol
.Replacement.ParagraphFormat.Shading.BackgroundPatternColorIndex = wdWhite
.Execute Replace:=wdReplaceAll
End With
End Sub