Blinking cells in Google Sheets

I am trying to get a cell to blink when a file is opened. I currently have the following code that I have found from here, but don't know how to modify it to blink when the file is open. Can anyone help?

function onEdit(e){var ss = SpreadsheetApp.getActiveSpreadsheet();var mysheet = ss.getSheetByName("LBACC17");var activeCell = ss.getActiveCell().getA1Notation();

if( activeCell == "K2" ){for(var i=0;i<50;i++){if( i%2 == 0 )mysheet.getRange("K3").setBackground("RED");elsemysheet.getRange("K3").setBackground("WHITE");

  SpreadsheetApp.flush();  Utilities.sleep(500);}

}}