Sub Macro1()
Dim oRng As Word.Range
  Selection.Find.ClearFormatting
  Selection.Find.Replacement.ClearFormatting
  Set oRng = ActiveDocument.Range
  With oRng.Find 'Selection.Find
    .Text = "([0-9]{1,})(:)([0-9]{1,})"
    .Replacement.Text = "\3\2\1"
    .Forward = True
    .Wrap = wdFindContinue
    .Format = False
    .MatchCase = False
    .MatchWholeWord = False
    .MatchAllWordForms = False
    .MatchSoundsLike = False
    .MatchWildcards = True
    .Execute Replace:=wdReplaceAll
  End With
End Sub