I imagine most office paper is white because it is easiest/cheapest to make. And ink is naturally black. Therefore white and black in real world, black and white on the computer screen. But it doesn't have to be that way.
I came across Zenburn theme. Surprisingly Googling Zenburn IntelliJ IDEA wasn't satisfactory. There is Zenburn theme for vim/kate/Eclipse/VStudio/... but not IDEA?
Just made my own theme based on Zenburn, it is in early stages but I think it is far better than the default.
Default

Zenburn

On a side note, Googling for a low contrast theme was non the less fruitful. There is a theme called Vibrant Ink. And the IntelliJ Theme for it here. I think it is a good choice as well.
