Dim sh As Worksheet
    For Each sh In Sheets(Array("Лист3", "Лист4"))
        With sh.UsedRange.Interior
            If .Color = vbRed Then .Color = vbBlue Else .Color = vbRed
        End With
    Next

Sub Ws_2_Col_test()
    '
    Dim col As New Collection

    Dim ws As Worksheet
    Set ws = ActiveSheet

    col.Add ws

End Sub

Dim x As Range
    For Each x In ThisWorkbook.Worksheets("Лист3").UsedRange
        If x.Interior.Color = vbRed Then x.Interior.Color = vbBlue
    Next

    For Each x In ThisWorkbook.Worksheets("Лист4").UsedRange
        If x.Interior.Color = vbRed Then x.Interior.Color = vbBlue
    Next

Option Explicit
Function UsedRangeByCodeName(sCodeName$) As Range
    Set UsedRangeByCodeName = ThisWorkbook.VBProject. _
        VBComponents(sCodeName). _
        Properties("usedrange").Object
End Function
Sub test()
    Dim MyCollection As New Collection
    Dim v, r As Range, r1 As Range, r2 As Range, addr$
    For Each v In Array("Лист3", "Лист4")
        MyCollection.Add UsedRangeByCodeName(CStr(v)), v
    Next
    With Application.FindFormat
        .Clear
        With .Interior
            .PatternColorIndex = xlAutomatic
            .Color = vbBlue
            .TintAndShade = 0
            .PatternTintAndShade = 0
        End With
    End With
    For Each r In MyCollection
        Set r1 = r.Find(What:="", After:=r(1, 1), LookIn:=xlFormulas, LookAt:= _
        xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:=False _
        , SearchFormat:=True)
        If Not r1 Is Nothing Then
            addr = r1.Address
            Set r2 = r1
            Do
                If r1.Address <> addr Then Set r2 = Union(r2, r1)
                Set r1 = r.Find(What:="", After:=r1, LookIn:=xlFormulas, LookAt:= _
                    xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:=False _
                    , SearchFormat:=True)
            Loop While Not r1 Is Nothing And r1.Address <> addr
        End If
        If Not r2 Is Nothing Then r2.Interior.Color = 255: Set r2 = Nothing
    Next
End Sub