I think we should share what we've been learning lately, as I often find techniques and styles in the community that I wonder how they are achieved. My most recent learnings in Photoshop and Illustrator are Gradient Map and the Blend tool.
in photoshop simply go Image > Adjustments > Gradient map, and your foregroud / background color are mapped accordingly. Very nice and simple results.
The Blend Tool
Have both objects selected. go, Objects > Blend > Blend Options >Specified steps> desired number
Select the objects again, go Object > Blend > Make. You can also move the anchor points around to make them overlap!