The following codes color a character in green. Is there any way to color a
string of variable size, e.g. "abc", "ha, ha, I got you" etc?

Sub GreenLetter()
Dim s As String * 1
Dim c As Range
Dim i As Long

s = InputBox("Which letter to greenden?")

If s Like "[!A-Za-z]" Then
MsgBox ("Must specify a LETTER")
Exit Sub
End If

For Each c In Selection
With c
If .HasFormula Then .Value = .Text
For i = 1 To Len(.Text)
If LCase(Mid(.Text, i, 1)) = LCase(s) Then
.Characters(i, 1).Font.Color = RGB(30, 255, 15)
'Selection.Interior.ColorIndex = [A1].Interior.ColorIndex
End If
Next i
End With
Next c
End Sub