Here is a VBA example that sets the cell colour
Private Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo ws_exit:
Application.EnableEvents = False
If Not Intersect(Target, Me.Range("A1:H10")) Is Nothing Then
With Target
Select Case UCase(.Value)
Case "b": .Interior.ColorIndex = 5
Case "o": .Interior.ColorIndex = 46
Case "p": .Interior.ColorIndex = 7
Case "r": .Interior.ColorIndex = 3
'etc.
End Select
End With
End If
ws_exit:
Application.EnableEvents = True
End Sub
'This is worksheet event code, which means that it needs to be
'placed in the appropriate worksheet code module, not a standard
'code module. To do this, right-click on the sheet tab, select
'the View Code option from the menu, and paste the code in.