시스템상에서 파랑색이 잘 안보입니다.

가장 좋은 방법은 default sheme 파일을 보고 수정하는 방법입니다.
locate default.vim
vi PATH/default.vim

PATH 에 보면 여러개의 sheme 파일이 있습니다.
보시면 뭔지 이해가실겁니다.

http://vimdoc.sourceforge.net/cgi-bin/vimfaq2html3.pl

22.3. How do I change the highlight colors to suit a dark/light background?

You can set the 'background' option to either 'dark' or 'light' to change
the highlight colors to suit a dark/light background:

:set background=dark

For more information, read

:help 'background'
:help 6.2

22.4. How do I change the color of the line numbers displayed when the
":set number" command is used?

The line numbers displayed use the LineNr highlighting group. To display
the current colors used, use

:hi LineNr

To change the color modify the LineNr highlight group. For example:

:hi linenr guifg=red guibg=black

This will give red numbers on a black background in GVIM.

For more information, read

:help :highlight

22.5. How do I change the background color used for a Visually selected
block?

You can modify the 'Visual' highlight group to change the color used for a
visually selected block:

:highlight Visual guibg=red

For more information, read

:help :highlight
:help hl-Visual

22.6. How do I highlight the special characters (tabs, trailing spaces, end
of line, etc) displayed by the 'list' option?

You can modify the "NonText" and "SpecialKey" highlight groups to highlight
the special characters displayed by the 'list' option:

:highlight NonText guibg=red
:highlight SpecialKey guibg=green

The "NonText" highlighting group is used for "eol", "extends" and
"precedes" settings in the "listchars" option. The "SpecialKey"
highlighting group is used for the "tab" and "trail" settings.

For more information, read

:help 'listchars'
:help hl-NonText
:help hl-SpecialKey