How can I give depth to my prints with different shades of blue?

The color and definition of your print will be affected by the exposure time and the density of the items you use. Try using semi translucent items for lighter shades of blue, such as very thin flower petals or a lace type scarf, or changing exposure time. E.g. Place all your items in full sun under your glass sheet and after several minutes remove some of the items to expose further, the areas that had shorter exposure time will give a lighter blue to the areas that had longer exposure time. Also take note of the time of day, your exposure time and the direction of the sun. Late afternoons will cast different shadows which can give a lovely gradient to your print. You can also explore doing prints of larger heavier objects and not placing a sheet of glass on top. This will mean the parts that have full contact with the page will make for white areas on your print, as appose to the areas that cast a shadow.