Here are a couple of solutions:
For text entries: (Change the "Text#" entries to meet your needs)
One way... copy the text below, press Alt+F11 to start the VBE Editor, then
double-click on the Sheet1 icon and paste this in:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim DropDownRange As Range
Dim ShadedRange As Range
If Target.Cells.Count > 1 Then Exit Sub
Set DropDownRange = Range("a1", Cells(Rows.Count, "a").End(xlUp))
If Intersect(Target, DropDownRange) Is Nothing Then Exit Sub
Set ShadedRange = Range(Cells(Target.Row, "a"), Cells(Target.Row, "N"))
With ShadedRange.Interior
Select Case (Target.Value)
Case "Text1": .ColorIndex = 36
Case "Text2": .ColorIndex = 37
Case "Text3": .ColorIndex = 38
Case "Text4": .ColorIndex = 39
Case "Text5": .ColorIndex = 40
Case "Text6": .ColorIndex = 41
Case Else: .ColorIndex = xlNone
End Select
End With
End Sub
..........................................
Or this for numerical entries.
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim DropDownRange As Range
Dim ShadedRange As Range
If Target.Cells.Count > 1 Then Exit Sub
Set DropDownRange = Range("a1", Cells(Rows.Count, "a").End(xlUp))
If Intersect(Target, DropDownRange) Is Nothing Then Exit Sub
Set ShadedRange = Range(Cells(Target.Row, "a"), Cells(Target.Row, "N"))
With ShadedRange.Interior
Select Case (Target.Value)
Case 1: .ColorIndex = 36
Case 2 To 10: .ColorIndex = 37
Case 11 To 15: .ColorIndex = 38
Case 16 To 25: .ColorIndex = 39
Case 25 To 50: .ColorIndex = 40
Case Is > 50: .ColorIndex = 41
Case Else: .ColorIndex = xlNone
End Select
End With
End Sub