I'm trying to simulate a blink of a label widget by changing its color in this manner: 

a) change to color #1, pause 1 sec, 

b) change to color #2, pause 1 sec, 

c) loop again using `tk.after` to rerun this procedure.

But the result is a constant color, #2.

`self.blink_status` is an index telling communication status is OK, and equals to `1`. of course code was tested with a constant value `self.blink_status=1` 

```
def blink_tx(self):
    if self.blink_status == 1:
        self.tx_label["bg"] = 'green'
        self.tx_value.set('Tx')
        sleep(1)
        self.tx_label["bg"] = 'blue'
        sleep(1)
    elif self.blink_status == 0:
        self.tx_label["bg"] = 'red'
        self.tx_value.set('*')
        sleep(2)
        self.tx_label["bg"] = 'orange'
    else:
        self.tx_label["bg"] = 'red'
        self.tx_value.set('x')
        sleep(2)

    self.status_frame.after(3500, self.blink_tx)

```

the way `self.tx_label` and `self.tx_value` are defined :

```
self.tx_label = tk.Label(self.status_frame, textvariable=self.tx_value, relief=tk.GROOVE, width=2)
self.tx_label.grid(row=0, column=4, sticky=tk.E)

```