Monochrome, the first thought that comes to a lot of people is a black and white picture. Some others think a bit more and realize that it basically means containing of a single colour tone. So technically, painting a rainbow to a sepia tone, will make it monochrome too, but then, that isnt what we want to show. When I say monochrome, I understand the picture to be made up of natural elements which share a common colour, in variation of shades. Let me show you what I mean.
Hope you like my point of view to monochrome.