Screen divider / border width and color

You can easily change statusline (the horizontal one) colors, by changing your caption string, in your ~/.screenrc. Given your screenshot, it looks like you are using the default one, so you may need to add in your ~/.screenrc:

caption always "my caption string"

You can replace always with splitonly, depending on whether you want it to always show or only if window is split, and you can customize the caption string using the escape codes listed in screen manual. As an example, putting %{= kw} at the beginning of it will change colors to white text on black background.

You can also find lots of others caption strings over the Internet, there are a lot of .screenrc findable with Google. I can give you the caption string I use, it shows user name, a nice list of screen windows, date, time, and system load, all these on a black background with not too bright colors.

caption always "%{= g}[ %{G}${USER}@%H%{g} ][%= %{= w}%?%-Lw%?%{r}(%{W}%n*%f %t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B} %d/%m %{W}%c:%s %{g}][%{Y}%l%{g}]%{=b C}%{W}"

Yes I know, the code is quite horrible, but with the screen documentation you should be able to adapt it or create a caption screen that matches your needs.

Concerning the vertical separators: I'm sorry I don't know how they will behave. Maybe they'll take the caption background color. I couldn't find documentation about it and I couldn't try it myself: the version of screen you are using dies miserably on my system with a screen caught signal 11 ...

@evilsoup: As you want a "distraction-free writing environment", you probably don't want any infos in the windows caption -- nothing but the default beckground color of your terminal, so use

caption string "%{= dd} "

This sets the back- and foreground color to default (d) and displays nothing (" ").

To get rid of the vertical bars, use the option proposed by @aaren:

rendition so "="

but do neither set the fore- nor the background color. This command works with screen 4.01.00devel, but with earlier (even <= 4.00) or non-devel versions you might need to use sorendition "=" instead.

When you add these lines to the screen config files as proposed by Stephane Chazelas on UL you should be fine: