Images 1 and 2: layers of the yellows and orange in the same way that I had described earlier.
Image 3: I have started putting in the folds here, this time wet-on-dry.
Image 4: In the area which I have marked `a`, you can see that one edge of the folds is hard and the other edge is soft: for this type of fold, apply the shadow color wet-on-dry and then soften the upper edge with a damp brush. You can also lift out a thin area of highlight on top of this fold. I have also added WN winsor red to my mixes in areas which tend towards a redder hue. You can also use it brighten your shadow color if it looks too dull. Schminke red madder dark is a dull red which I have used in shadows, Winsor and Newton winsor red is a nice red which is not cool like Schminke´s ruby red.
Image 5: A large shadow here made by the petal behind the main one. You can do this wet-on-dry softening any edges if required. The top and bottom areas of the petal marked `a` and `b` are darker, add a little more of blue and red madder dark to the mix and add this while the wash is still wet. Add creases now with a darker shadow color. You can also do them later when the petal is completely dry: Add them wet-on-dry and run a damp brush over them to soften the edges. The edges of the large bottom petal tend towards red. Leave out highlights in all the layers, you can tint them later.
Image 6: The area marked `a`has some winsor red and tends a lot towards red.
Image 7: The area marked `a` is a shadow color, if you make this too bright, it will pop forward and wont give you that cup shape over there.
In general, I have first wet the petal gently (being careful not to disturb the previous layers), put in a shadow color whereever soft edges are required and then put in the darker shadows and also shadows having harder edges. Study the petal carefully before wetting it and then lay in the colors confidently without fumbling, as going back and forth is sure to ruin the wash. It doesn´t matter if you don´t paint the folds exactly as you see them; you only have to get a feel for the three dimensional form and get that sense into what you are creating.
Paint the shadows on the butterfly created by the two wings overlapping each other, where they don´t overlap you should be able to see some nice bits of clean yellow of the first layers shining. The shadow colors tend towards green (specially the top wing) and some towards orange.
Here´s the photo that I had taken on a nice, sunny day at the market: