Vim正常背景更改前景文本颜色

Question

I'm trying to standardize terminal colors in my vim theme and I came across some odd behavior about how Vim appears to handle foreground text color depending on background colors.

Consider this very simple vim theme:

if exists("syntax_on")
  syntax reset
endif

set t_Co=256

highlight Normal ctermfg=NONE ctermbg=234 cterm=NONE
highlight PreProc ctermfg=197 ctermbg=NONE cterm=NONE

It's not very pretty (as a simple example) but it looks like this:

If I then change one line setting Normal to ctermbg=NONE like so:

highlight Normal ctermfg=NONE ctermbg=NONE cterm=NONE

I get something that looks like this:

As you can see, the background clearly changes (as expected), but the foreground color changes as well.

Why is changing this property in vim causing this behavior? How can I remove the background without changing the foreground colors?

I'm using the default terminal in OS X with 256 bit color enabled.

I appreciate the help!

Answer 1

That behavior is normal, expected, and explained in :hi-normal-cterm .

Basically, the value of the background option is used to define a bunch of default colors for different highlight groups and that option is redefined whenever you change the Normal highlight group.

To force a value for background , add this line to your colorscheme:

set background=dark

or:

set background=light

Also, there's no reason whatsoever to put set t_Co=256 anywhere in any vim script.