Winning Loop Connect 4
Typically, a Swing application would be written using a Model-View-Controller pattern to split the responsibilities:


The Model would be a data structure to represent the game state.  It could, for example, consist of an ConnectFourBoard class that holds a two-dimensional array of chips in the board.
The View would be the Swing UI code
The Controller acts as the glue between the Model and View.  It handles actions triggered by the View, and notifies the View when the Model has changed.


Here, I see View and Controller code, commingled.  However, I don't see any Model code.  In fact, in ColButton.actionPerformed(), it appears that the lack of a Model is causing you some difficulty: you're resorting to determining the model state by parsing the icon name out of the view.

Without a Model, you are no doubt going to have a difficult time examining the model state to determine the winner.