Here is better code that fixes the border coloring issue. Place this behind Sheet1 for ex.
or we can change the code to run from a module on all sheets.

VB Code:
  1. Private Sub Worksheet_SelectionChange(ByVal Target As Range)
  2.     If Range("E39").Value < 100 Then
  3.         With Range("G39").Interior
  4.             .ColorIndex = 3
  5.             .Pattern = xlSolid
  6.             .PatternColorIndex = xlAutomatic
  7.         End With
  8.     Else
  9.         With Range("G39")
  10.             .Interior.ColorIndex = 0
  11.             .Interior.Pattern = xlSolid
  12.             .Interior.PatternColorIndex = xlAutomatic
  13.             .Borders(xlDiagonalDown).LineStyle = xlNone
  14.             .Borders(xlDiagonalUp).LineStyle = xlNone
  15.             .Borders(xlEdgeLeft).LineStyle = xlNone
  16.             .Borders(xlEdgeTop).LineStyle = xlNone
  17.             .Borders(xlEdgeBottom).LineStyle = xlNone
  18.             .Borders(xlEdgeRight).LineStyle = xlNone
  19.             .Interior.ColorIndex = xlNone
  20.         End With
  21.     End If
  22. End Sub