Hi Elen, I'm glad it is making more sense. Don't worry about not seeing cool pink on a grapefruit -- you see, you're training your brain to perceive differently from before, and it takes a while for the ole brain to 'get it'. I've trained my not artistic cerebral husband to see colours, not actively 'trained', but by exclaiming "oooo, look at that gorgeous turquoise light in the leaf". His perception before was simply red, yellow, blue, green, and everything else was 'brown'... well, maybe grey too...
What to do to see colours better: Be relaxed (do not stare), let your gaze move over the whole set-up, and beyond it too. Let your eyelids droop, squint. Try blinking rapidly, and some colours will 'flash'.
And search for colours wherever you are, sitting in a bus, for example. Try to give a name to what you actually *see*. Say a stop is next to a building, where you can see both sides of a corner. Say they're both in shadow. The part facing the street may be a bit bluer than the part facing the lawn which will look slightly greener due to reflected light from the grass. Compare. Ask, which is bluer, which is greener, which is more violet? Is this a pure grey, or is it a blue-ish gray, or a greenish-gray?
Reading lessons and advice will not make much sense until you have to actually *use* it. Have tried to use it, and discovered you do not really know it. Then when you go back and re-read, you'll discover that it was in the text all the time!

In fact, the next time you go through the text of stage 2, for example, you'll discover something new again. We're simply more receptive and more ready to internalize it, and it usually happens bit by bit. (I discovered totally new things when preparing for this class, and I've used this method exclusively since 2003, and studied really hard... )
Basically, relax, let it grow on you, search actively for colour, and suddenly one day you'll just see! It feels like magic! But it truly is just that the brain 'got it', finally. But the 'magic' is there, and the world will never look the same, as it now will be shimmering with gorgeous colours. For me personally, even after the magical moment, the old way of seeing kept interfering, and I sort of flipped between the two. Then it stabilized, within the colourful universe. Funny how something so simple, really, as becoming aware of what has always been there can transform the world.
Elen, very wise of you to stay with the simple things for a while, I support that wholly. Maybe you can take a block form (small carton, a book, or wrap a box in coloured paper) plus a round object and paint those. A cone or a cylinder woud do as well as a sphere. These are the basics of any forms you see in nature, so discovering and studying how light and colour behave on these will serve you for *any* kind of subject. A roll of toilet paper is a great handy cylindrical object, and the empty roll can be painted or wrapped. It can be laid down, or stand up, in a set-up. I painted numerous such simple studies, just to learn to see and to paint what I saw. Had great fun combining colours in all sorts of ways. So yes, the more studies, the better one learns, and the better a 'real' painting will be when one eventually gets to it.
So please make a simple study, and post each stage and I'll guide you through the mystery of it.
Charlie