Slows Down When The Range Is Expanded

Is there a faster method than this code? it slows way down when the range is expanded b/c it loops through every cell.

Private Sub Worksheet_SelectionChange(ByVal target As Range)
If target.Cells.Count > 1 Then Exit Sub
Set Rng = Range("A1:GA400")
clrind = 42
If Not Intersect(target, Rng) Is Nothing Then
For Each cell In Rng
If cell.Interior.ColorIndex = clrind Then cell.Interior.Pattern = xlNone
Next cell
End If
End Sub