You can use VBA code like this - it will affect current selection (if the selection is a Range of cells
Option Explicit Public Sub setBorders() Dim cel As Range, clr1 As Long, clr2 As Long clr1 = vbWhite 'if cell border color is different than white, and has LineStyle clr2 = vbRed 'change its color to vbRed If TypeOf Selection Is Range Then For Each cel In Selection 'select your Range With cel With .Borders(xlEdgeLeft) If .Color <> clr1 And .LineStyle <> xlNone Then .Color = clr2 End With With .Borders(xlEdgeTop) If .Color <> clr1 And .LineStyle <> xlNone Then .Color = clr2 End With With .Borders(xlEdgeBottom) If .Color <> clr1 And .LineStyle <> xlNone Then .Color = clr2 End With With .Borders(xlEdgeRight) If .Color <> clr1 And .LineStyle <> xlNone Then .Color = clr2 End With End With Next End If End Sub
To use it open the VBA editor - Alt + F11, and paste the code in a standard VBA module