Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column <> 3 Then Exit Sub
If UCase(Target.Value) = "X" Then
If Target.Offset(0, -1).Interior.Color = 15773696 Then
Target = ""
Else
Target.Offset(0, -1).Interior.Color = 5296274
End If
Else
If Not Target.Offset(0, -1).Interior.Color = 15773696 Then
Target.Offset(0, -1).Interior.Color = xlNone
End If
End If
End Sub