Improve .vimrc glyphs and highlight colors

vim/.vimrc

@@ -1,5 +1,5 @@
 set t_ut=''
-let s:is_color = &t_Co >= 16
+let s:is_color = &t_Co >= 256
 set hidden
 set splitbelow
 set splitright
@@ -12,22 +12,29 @@ set list
 let &fillchars = "vert:\u2502,fold: ,diff:\u00b7"
 if s:is_color
     autocmd ColorScheme * highlight error cterm=none ctermbg=darkred
-        \ ctermfg=lightgray
+        \ ctermfg=black
     autocmd ColorScheme * highlight InvalidWhitespace ctermbg=black
+    autocmd ColorScheme * highlight LineNr ctermfg=darkgray
     autocmd ColorScheme * highlight Overlength ctermbg=black
-    autocmd ColorScheme * highlight Pmenu ctermbg=darkblue ctermfg=lightgray
-    autocmd ColorScheme * highlight PmenuSel ctermbg=lightgray ctermfg=darkblue
-    autocmd ColorScheme * highlight Search ctermbg=darkblue ctermfg=lightgray
-    autocmd ColorScheme * highlight SignColumn ctermbg=black ctermfg=darkblue
+    autocmd ColorScheme * highlight Pmenu ctermbg=darkblue ctermfg=black
+    autocmd ColorScheme * highlight PmenuSel ctermbg=lightgray ctermfg=black
+    autocmd ColorScheme * highlight Search ctermbg=darkblue ctermfg=black
+    autocmd ColorScheme * highlight SignColumn ctermbg=none ctermfg=darkblue
     autocmd ColorScheme * highlight SpellBad ctermbg=darkmagenta
-        \ ctermfg=lightgray
+        \ ctermfg=black
     autocmd ColorScheme * highlight SpellCap ctermbg=darkmagenta
-        \ ctermfg=lightgray
+        \ ctermfg=black
     autocmd ColorScheme * highlight StatusLine cterm=bold ctermbg=black
         \ ctermfg=lightgray
     autocmd ColorScheme * highlight StatusLineNC cterm=none ctermbg=black
         \ ctermfg=none
-    autocmd ColorScheme * highlight todo ctermbg=none ctermfg=darkblue
+    autocmd ColorScheme * highlight SyntasticError ctermbg=darkred
+        \ ctermfg=black
+    autocmd ColorScheme * highlight SyntasticErrorSign ctermfg=darkred
+    autocmd ColorScheme * highlight SyntasticWarning ctermbg=darkyellow
+        \ ctermfg=black
+    autocmd ColorScheme * highlight SyntasticWarningSign ctermfg=darkyellow
+    autocmd ColorScheme * highlight todo ctermbg=none ctermfg=darkyellow
     autocmd ColorScheme * highlight VertSplit cterm=none ctermfg=black
     autocmd ColorScheme * highlight Visual cterm=none ctermbg=darkgray
     colorscheme peachpuff
@@ -80,7 +87,7 @@ endif
 let airline_theme = s:is_color ? 'powerlineish' : 'monochrome'
 let airline_detect_spelllang = 0
 let airline#extensions#tabline#enabled = 1
-let airline_symbols = {'modified': " \u2022", 'linenr': '', 'maxlinenr': ''}
+let airline_symbols = {}
 if s:is_nerd_font
     if s:is_color
         let airline_powerline_fonts = 1
@@ -91,16 +98,14 @@ if s:is_nerd_font
         let airline#extensions#tabline#right_alt_sep = "\ue0b3"
     endif
     let airline_section_z = "\uf13a %l/%L \uf138 %c"
-    let airline_symbols.crypt = "\uf09c"
+    let airline_symbols.crypt = "\uf805 "
     let airline_symbols.paste = "\uf691"
-    let airline_symbols.spell = "\uf9c5"
+    let airline_symbols.spell = "A\uf62b"
     let airline_symbols.branch = "\uf418"
-    let airline_symbols.notexists = " \ufc50"
     let airline_symbols.readonly = "\uf023 "
     let airline_symbols.whitespace = "\uf038"
-    let airline#extensions#tabline#overflow_marker = "\u2026"
-    let syntastic_error_symbol = "\ufc65 "
-    let syntastic_warning_symbol = "\uf525 "
+    let syntastic_error_symbol = "\ue231 "
+    let syntastic_warning_symbol = "\uf071 "
     let syntastic_style_error_symbol = "\ue245 "
     let syntastic_style_warning_symbol = "\ue245 "
 else
@@ -108,21 +113,27 @@ else
     let airline_right_alt_sep = "\u2502"
     let airline#extensions#tabline#left_alt_sep = "\u2502"
     let airline#extensions#tabline#right_alt_sep = "\u2502"
-    let airline_section_z = "\u25bc %l/%L \u25ba %c"
+    let airline_section_z = "\u2193%l/%L \u2192%c"
+    let airline_symbols.crypt = 'CRYPT'
+    let airline_symbols.spell = "A\u221a"
     let airline_symbols.branch = ''
-    let airline_symbols.notexists = ''
     let airline_symbols.readonly = 'ro'
     let airline_symbols.whitespace = ''
-    let syntastic_error_symbol = "!\u25ba"
-    let syntastic_warning_symbol = "!\u25ba"
-    let syntastic_style_error_symbol = "s\u25ba"
-    let syntastic_style_warning_symbol = "s\u25ba"
+    let syntastic_error_symbol = "!\u2192"
+    let syntastic_warning_symbol = "!\u2192"
+    let syntastic_style_error_symbol = " \u2192"
+    let syntastic_style_warning_symbol = " \u2192"
 endif
+let airline_symbols.modified = "\u2022"
+let airline_symbols.notexists = "\u2022"
+let airline_symbols.linenr = ''
+let airline_symbols.maxlinenr = ''
 let airline#extensions#tabline#show_tabs = 0
 let airline#extensions#tabline#show_tab_type = 0
 let airline#extensions#tabline#buffer_nr_show = 1
 let airline#extensions#tabline#buffer_nr_format = "%u "
 let airline#extensions#tabline#formatter = 'unique_tail_improved'
+let airline#extensions#tabline#overflow_marker = "\u2026"
 let airline#extensions#tabline#tab_nr_type = 1
 let airline#extensions#tabline#show_close_button = 0
 let airline#extensions#wordcount#enabled = 0