Hi,

It cannot be done with formulas but with VBA :

Private Sub Worksheet_Change(ByVal Target As Range)
Set Target = Range("A1")
With Target.Characters(Start:=1, Length:=4).Font
.ColorIndex = 3
End With
With Target.Characters(Start:=5, Length:=12).Font
.ColorIndex = 5
End With
End Sub

HTH