You are stuck with VBA. Event code would do the trick.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim Num As Long
Dim rng As Range
Dim vRngInput As Variant
Set vRngInput = Intersect(Target, Range("A:A"))
If vRngInput Is Nothing Then Exit Sub
For Each rng In vRngInput
'Determine the color
Select Case rng.Value
Case Is = 1: Num = 6 'yellow
Case Is = 2: Num = 10 'green
Case Is = 3: Num = 5 'blue
Case Is = 4: Num = 3 'red
Case Is = 5: Num = 46 'orange
End Select
'Apply the color
rng.Interior.ColorIndex = Num
Next rng
End Sub
Alternative solution........download Bob Phillips' CFPlus add-in. Allows up to
30 conditions.
http://www.xldynamic.com/source/xld.CFPlus.Download.html
To implement the above event code right-click on the sheet tab and "View Code"
Copy/paste the code into that sheet module.
As you change the numbers in column A the background color will follow.
Adjust to suit.
Gord