Making changes to individual frames

I might have asked this one before, but I don’t see an option to view previously asked questions, so here goes - I am trying to find out how to make changes to individual frames. I think I have tried everything possible, keyframes, constant vs non-constant segments, drawing view, scene planning, default etc., except for adding still another drawing elements, which I think would be very awkward just to add a subtle change which would go over a few frames.

Let me explain; I have a face. It is talking. On a certain point I want to add a blush to its cheeks. It is embarrassed.
But if I try to add a little touch of colour to one frame, ALL frames are changed. From the beginning to the end. And it obviously doesn’t matter what I try to do - so what is the secret? I am sure it is rather obvious but it escapes me.

If this would behave like a normal timeline with frames, you should be able to make such changes to any single frame and only that frame would be changed. What is the idea behind the behaviour which one sees here - that if you make a change to one frame, all are changed?

I know that I could make another version of the face and paste it as a new drawing in the timeline, but hey, that seems to me a very clumsy way to get things done, don’t you think? I hope there is a trick which makes it possible to work on whichever frame one wants, without affecting all thousand of them!;action=display;threadid=5586;start=msg21913#msg21913

I knew it! I had asked before and it was simple ;D Thanks a lot!