There are six phases of Musicolor Notation. The first is what you have in Volume 1 of Piano For Kids. Volume 2 is Phase 2, Vol 3 is Phase 3 and etc, all the way to Phase 6.
The sixth phase of Musicolor Notation is with traditional notation using colored noteheads.
Depending on the child’s age and aptitude, I begin using a traditional method book like a workbook around Phase 2 or 3 in parallel with playing more complex pieces accessible through Musicolor Notation.
This is explained in detail in the Masterclass. In short, students identify one note throughout the piece and begin coloring them throughout. This begins the process of having them recognize where the notes live on the staff - but after they are already enjoying the music-making process. This is reserved for just 5 to 10 minutes of each lesson.
It takes a long time to read music just as it takes a long time to read words. But in my 12 years of teaching this way, we have had so many kids move through the entire process. You can see/hear some of our student recitals here: https://www.parkslopemusiclessons.com/videos/