'Your code to select range goes here
.ColorIndex = 3 'choose number for appropriate colour
.Pattern = xlSolid
Range("A1").Comment.Visible = False
Range("A1").Comment.Text Text:="User Name:" & Chr(10) & "Comment Text" & Chr(10) & ""
Here's some code that will do as you requested. You will need to tweak the inputbox comment, and the colorindex value.
Dim Cell As Range, FirstCell As Range, First As Boolean, Contents As String
First = True
For Each Cell In Selection
If First = True Then
Set FirstCell = Cell
First = False
Contents = Contents & " " & Cell
Selection.Interior.ColorIndex = 12
FirstCell = Contents & " " & InputBox("User Comment")