|Phones Lined up by Alexa Fotos|
The color harmony while random might be close or similar to a monochromatic scheme. Despite the other telephones having some black, in some ways it could have a bit of very dark green. The background, however, does aid the scheme by adding a variety of greens to make the background and foreground look interesting.It's possible the objects are showing depth by proximity as each object is behind one another (slightly).
Source: Alexa_Fotos. "Free Image on Pixabay - Phone, Models, Generations, Old." Phone Models Generations · Free Photo on Pixabay. Pixabay, 11 Sept. 2016. Web. 25 Apr. 2018. <https://pixabay.com/en/phone-models-generations-old-1662191/>.