# let's say we have a few graphic collections, this could work with just regular Graphics too 
# but you can worry about that later

image_graphic
contours_graphic  # LineCollection
temporal_stack  # LineStack

GraphicCollectionColorState:
  """stores state of a graphic collection's colors"""
  def __init__(self, collection: GraphicCollection):
    self._collection = collection

    # used to store state of graphic prior to being selected
    self._previous_states = [None] * len(self._collection)

  def set_selected(self, index: int):
    self.reset()

  def add_to_selected(self, indices: np.ndarray[int]):
    # not sure if this will work but we can make it work
    self._previous_states[indices] = self._collection[indices].colors

    # "highlight" these graphics
    self._collection[indices].colors = "w"

  def remove_from_selected(self, indices: np.ndarray[int]):
    # reset them back to the original state
    self._collection[indices].colors = self._previous_states[indices]
    self._previous_states[indices] = None

  def reset(self):
    for i in range(len(self._previous_states)):
      if self._previous_states[i] is not None:
        self._collection[i].colors = self._previous_states[i]
        self._previous_states[i] = None

contours_state = GraphicCollectionColorState(contours_graphic)
temporal_state = GraphicCollectionColorState(temporal_stack)

# simple 
def image_clicked(ev):
  # if shift key is held
  if "Shift" in ev.modifiers
    contours_state.add_to_selected(index_from_euclidean)
    temporal_state.add_to_selected(index_from_euclidean)
  else:
    contours_state.set_selected(index_from_euclidean)
    temporal_state.set_selected(index_from_euclidean)

# the repetitive code where the same state is set for contours and temporal could be removed by having 
# GraphicCollectionColorState manage a list of GraphicCollection as well instead of just a single one

def temporal_stack_clicked(ev):
  if "Shift" in ev.modifiers
    contours_state.add_to_selected(index)
    temporal_state.add_to_selected(index)
  else:
    contours_state.set_selected(index)
    temporal_state.set_selected(index)