I like to use a lot of Blending Modes, Opacities and restricted palettes in my work. Sometimes it can get a little monotonous even though the end result can be very pleasing.
To mix it up, I decided to challenge myself by creating a greyscale portrait that underneath a top shape of Blending Mode
Color with a black fill, it was full of randomly picked colours. The challenge was to tweak the Opacity and Blending Mode for each colour used to fit the portrait. The black fill on top was always enabled, so you didn't really get to see the bizarre colouring underneath until the end.
A challenging yet fun project to try and it really pushes your technical skill set with using Blending Modes and Opacities. Try it yourself.