For this section of the painting I have added a medium wash in French Ultramarine Blue to the napkin. The napkin is plaid, so I will have several washes to glaze on to make the total effect. I used a very wet wash and the puddles actually help to glaze shadow and texture in this wash. I used darker values behind the apple and on the edges of folds.
It's good to squint your eyes to better see the values in your reference photos.