Change Font Colour in Autoshape

Try below Code

Option Explicit
Dim MyShape As Shape
Private Sub Worksheet_Change(ByVal Target As Range)
    If Not Intersect(Target, Range("A1")) Is Nothing Then
    
        Set MyShape = ActiveSheet.Shapes(1)
        
        With MyShape.TextFrame.Characters.Font
            If Range("A1") = 1 Then
                .Color = 2             'Black
            ElseIf Range("A1") = 2 Then
                .Color = 5287936       'Green
            ElseIf Range("A1") = 3 Then
                .Color = 15773696      'Blue
            Else
                .Color = 65535         'Yellow
            End If
        End With
    End If
End Sub

How to use:

1. Copy above code.
2. Right Click to the sheet and select View Code
3. Paste code into the right pane.
4. Press Alt + Q to close the VBE.
5. Save workbook before any other changes.