This is the Portrait of Greta Moll by Henri Matisse, painted in 1908. You can see a woman sitting in front of a blue and white toile de Jouy patterned fabric, which was a favourite studio prop for Matisse and appears in many of his paintings from this period. The fabric determined not only the background but also the final choice of colours for the entire painting.
Greta Moll herself was a sculptor who had previously been a student in Berlin, where her portrait had been painted by Lovis Corinth. When Matisse saw a photograph of that portrait and didn't like it, he offered to paint his own portrait of her - no obligation to buy if she or her husband weren't satisfied.
It's interesting to note how Matisse deliberately placed pure colours next to each other for maximum effect, inspired by the example of Georges Seurat. However, the pose and smooth, rounded forearms were influenced by a 16th-century portrait in the Louvre, Veronese's Woman and Child with a Dog.
Despite the apparent simplicity of this painting, Greta had to pose for ten three-hour sessions before Matisse completed it.
Portrait of Greta Moll hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.