Private Sub Routine is not functioning

Sameer_Kuppanath_Sultan 

I don't see any issues with your code. By chance, do you have other event procedures, such as "selection_change"?

Another thing you could try, is setting a break point in your code (click in the gray area to the left and you see a circle with the line highlighted - click again to remove it). When your code runs, it will stop on this line. Then, you can hit the F8 key to step through it and follow the flow of your program. Perhaps it will help identify where the issue is.

Sameer_Kuppanath_Sultan 

Your code is fine and it should work as you haven't disabled Events in your change event code.
Is there any other code where you have disabled the Events with the following line?
Application.EnableEvents = False

If so please make sure that you enable the Events again before the End Sub or Exit Sub if any in your code.

Btw try this version and see if this works for you. This is a workaround but you will have to figure it out why Events are being disabled. To check that when your code stops working, open the Immediate window by pressing Ctrl+G and type ?Application.EnableEvents in there and hit Enter.
What do you get in the Immediate Window, a True or a False?

Private Sub Worksheet_Change(ByVal Target As Range)
MyVal = Range("Total4").Value

On Error GoTo Skip

With ActiveSheet.Tab
Select Case MyVal
Case Is > 0
.Color = vbBlack
Case Is = 0
.Color = vbRed
Case Else
.ColorIndex = xlColorIndexNone
End Select
End With

If Not Intersect(Target, Me.Range("b:b")) Is Nothing Then
    Target.Offset(0, 1).Activate
ElseIf Not Intersect(Target, Me.Range("c:c")) Is Nothing Then
    Target.Offset(1, -1).Activate
End If

If Not Intersect(Target, Me.Range("e:e")) Is Nothing Then
    Target.Offset(0, 1).Activate
ElseIf Not Intersect(Target, Me.Range("f:f")) Is Nothing Then
    Target.Offset(1, -1).Activate
End If

If Not Intersect(Target, Me.Range("h:h")) Is Nothing Then
    Target.Offset(0, 1).Activate
ElseIf Not Intersect(Target, Me.Range("i:i")) Is Nothing Then
    Target.Offset(1, -1).Activate
'OB
End If

If Not Intersect(Target, Me.Range("d18")) Is Nothing Then
    Target.Offset(-6, 0).Activate
ElseIf Not Intersect(Target, Me.Range("d12")) Is Nothing Then
    Target.Offset(-1, 0).Activate
End If

If Not Intersect(Target, Me.Range("d11")) Is Nothing Then
    Target.Offset(7, 3).Activate
ElseIf Not Intersect(Target, Me.Range("g18")) Is Nothing Then
    Target.Offset(-6, 0).Activate
End If

If Not Intersect(Target, Me.Range("g12")) Is Nothing Then
    Target.Offset(-1, 0).Activate
ElseIf Not Intersect(Target, Me.Range("g11")) Is Nothing Then
    Target.Offset(3, -3).Activate
End If

If Not Intersect(Target, Me.Range("d22")) Is Nothing Then
    Target.Offset(0, 3).Activate
ElseIf Not Intersect(Target, Me.Range("g22")) Is Nothing Then
    Target.Offset(1, -3).Activate
End If

If Not Intersect(Target, Me.Range("d16")) Is Nothing Then
    Target.Offset(-3, 3).Activate
ElseIf Not Intersect(Target, Me.Range("g16")) Is Nothing Then
    Target.Offset(0, -3).Activate
End If

If Not Intersect(Target, Me.Range("d20")) Is Nothing Then
    Target.Offset(-1, 0).Activate
ElseIf Not Intersect(Target, Me.Range("d19")) Is Nothing Then
    Target.Offset(1, 3).Activate
End If

If Not Intersect(Target, Me.Range("g20")) Is Nothing Then
    Target.Offset(-1, 0).Activate
ElseIf Not Intersect(Target, Me.Range("g19")) Is Nothing Then
    Target.Offset(1, -3).Activate
End If

If Not Intersect(Target, Me.Range("d10")) Is Nothing Then
    Target.Offset(-1, 0).Activate
ElseIf Not Intersect(Target, Me.Range("d9")) Is Nothing Then
    Target.Offset(-1, 0).Activate
End If

If Not Intersect(Target, Me.Range("d8")) Is Nothing Then
    Target.Offset(2, 3).Activate
ElseIf Not Intersect(Target, Me.Range("g10")) Is Nothing Then
    Target.Offset(-1, 0).Activate
End If

If Not Intersect(Target, Me.Range("g9")) Is Nothing Then
    Target.Offset(-1, 0).Activate
ElseIf Not Intersect(Target, Me.Range("g8")) Is Nothing Then
    Target.Offset(0, -3).Activate
End If

If Not Intersect(Target, Me.Range("d26")) Is Nothing Then
    Target.Offset(0, 3).Activate
ElseIf Not Intersect(Target, Me.Range("g26")) Is Nothing Then
    Target.Offset(0, -3).Activate
End If
Skip:
Application.EnableEvents = True
End Sub