This is my favorite color theme for Vim, self-made based on some existing themes (can't even recall which ones). Feel free to use it anyway you like. Usually you will want to put it into your
~/.vim/colors/ directory and then select using the colorscheme command in Vim. Here's the file: amber.vim. Recently I'm using a different scheme, also monochromatic, but green this time: sheep_green.vim.
Looking at available "simple" text editors I recently rediscovered Gedit, GNOME's default text editor. It's actually very cool: has simple and straightforward interface, syntax highlighting, incremental search, uses GTK2 so looks good on my desktop, can be extended using plugins written in Python and with some additional plugins installed can actually edit text pretty efficiently (I still miss a "kill word" command though).
One problem I had is that all the code highlighting color themes look pretty much like a mad fruit salad – seems like the authors made it a point of honor to never use the same color twice. I had to write my own theme: sheep.xml. To use it, just put that file into
.local/share/gtksourceview-2.0/styles/ directory in your home – the style should appear in Gedit's preferences. It only uses one color (and several shades of gray) and I made it so that changing that color is very simple – so you can make it match your desktop theme.