As promised yesterday here is the image of the series of Matisse photographs documenting the progress of the painting The Pink Nude, 1935
https://www.wikiart.org/en/henri-matisse/pink-nude-1935
I took it as a screen shot form one of my lectures and so quality not perfect but you can read at the bottom of each image the date of the work and you can see he worked on this for a long long time!!!! And how much transformation! So it is a good lesson to be fearless! And to not worry of the process takes time!
Paintings can definitely change yes and this transformation I also think is to do with the magic that happens in between as the artist can never be fully sure of anything... even something as planned as a miniature. I've just finished a large miniature that had gilding done in the middle of it and the sky changed 3 times from blue, to green, to yellow eventually - until it felt right, basically.
Matisse is great, he was also inspired by Persian miniatures!