Bonjour, une autre proposition :
Option Explicit
Sub Couleur_L()
Dim i As Long, nL As Long, celVal As Single
Dim couleur(3) As Long, wS As Worksheet, index As Byte
Set wS = Sheets("Données")
couleur(1) = RGB(226, 239, 218)
couleur(2) = RGB(255, 242, 204)
couleur(3) = RGB(255, 124, 128)
nL = wS.Cells(Rows.Count, "L").End(xlUp).Row
For i = 3 To nL
If IsNumeric(wS.Cells(i, 12)) Then
celVal = wS.Cells(i, 12).Value
Select Case celVal
Case Is < 100: index = 1
Case Is > 500: index = 3
Case Else: index = 2
End Select
wS.Cells(i, 12).Interior.Color = couleur(index)
End If
Next i
End Sub