Vim split bar styling

You'll need to edit your colorscheme. The highlight group is VertSplit.

If you want to get rid of the pipe characters you can set ctermbg and ctermfg to the same value.

Additional information on styling vertical split borders*:

*Taken from ib. answer below.

In order to get rid of | characters, one should rather change vertical separator using:

:set fillchars+=vert:\ 

(note the significant whitespace after the '\' character)

highlight VertSplit cterm=NONE

I kind of tweak it a little to make it look like there is no splitbar with something like this

hi LineNr guibg=bg
set foldcolumn=2
hi foldcolumn guibg=bg
hi VertSplit guibg=bg guifg=bg

Note that I'm using gvim so I'm using guibg to change the background guifg to change the foreground with the same color of my vim's background, if you're not using a gui and you're on terminal vim you should change the guibg and guifg parameters for ctermbg and ctermfg