Refreshing the repeat insertion of characters

[Heime]

I want to insert the letter "B" followed by a space using the function 
"ticker-second".
The adaptation is to start inserting from a certain position (row col) in a 
buffer.

Repeat "ticker-second" for 4 repeats, clear the previous inserts and start 
again.


(defun ticker-second (lampkl)
  "TODO."

  (interactive)

  (cond
   ((eq 'blue lampkl)
       (insert (propertize "B"
                  'font-lock-face '(:background "blue"
                                    :foreground "white"))))

   ((eq 'green lampkl)
       (insert (propertize "G"
                  'font-lock-face '(:background "green"
                                    :foreground "white")))))

  (insert " "))


(defun fire-clock ()
  "TODO."
  (interactive)
  (run-with-timer 0 4 #'firefly-ticker-second 'blue))