Option Explicit
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If Target.Column = 2 Then
If Cells(Target.Row, 2).Interior.ColorIndex = 4 Then
Union(Cells(Target.Row, 2), Cells(Target.Row, 1), Cells(Target.Row, 3)).Interior.ColorIndex = xlNone
Else
Union(Cells(Target.Row, 2), Cells(Target.Row, 1), Cells(Target.Row, 3)).Interior.ColorIndex = 4
End If
End If
End Sub