Step 6 Now we need to give more depth and some rich, subtle colour to the background (here, the waves). One of the simplest ways to do this is to duplicate the wave layer several times, and set each duplicate layer’s blending mode to Multiply.
Step 7 Now set the opacity of each of these wave layers to between 25% and 30%, and start adding colour on each of these layers. The aim is to create a shifting, deep backdrop with subtly varied colours.
Step 8 Now turn your attention to the objects. Make all the layers for the waves invisible, then add a new layer and load the mask for the objects that you created in step 3 (Select > Load Selection). Define the shapes by filling them with red.
Step 9 Now turn on all the layers you created for the background (here, the waves) and move the layers for the objects slightly, to create that offset effect.