Couldn't get the BG to change using the constant vbRed, but declaring a long worked.
Try this:
Code:
Private Sub quantiteSortiO_AfterUpdate()
Dim ts As Integer
Dim lngRed As Long, lngWhite As Long
lngRed = RGB(255, 0, 0)
lngWhite = RGB(255, 255, 255)
Me.Texte15 = Me.Texte15 - Me.quantiteSortiO
ts = DLookup("[minimum]", "Stock", "[produitId] = " & Me.Modifiable27)
'is less than
If Me.Me.quantiteSortiO < ts Then '<<-- shouldn't this be Me.Texte15 ???
Me.Étiquette29.Caption = "Red"
Me.Étiquette29.BackStyle = 1
Me.Étiquette29.BackColor = lngRed
' Me.Étiquette29.BorderStyle = 1
Else
'is greater than or equal to
Me.Étiquette29.Caption = "White"
Me.Étiquette29.BackStyle = 0
Me.Étiquette29.BackColor = lngWhite
' Me.Étiquette29.BorderStyle = 0
End If
End Sub