You could insert the lines directly in a callback. Or you call this function from the callback and provide a handle to an axes, which is created inside the GUI:
function YourCallback(ObjectH, EventData, handles)
Untitled(handles.axes1);
end
Now use the provided axes handle as Parent object for the displayed images, e.g.:
function Untitled(AxesH)
...
imshow(red, 'Parent', AxesH);
Omit e.g. subplot(1,2,1) then.
By the way: The shown code is hard to read and to understand. The lack of comments and orphaned variables (output_args? input_args? hp = impixelinfo(); but you do not export hp?) reduce the quality and usability of the code massively.