How to define my own highlight colors to use with matchadd() in vim?

I recently found this little piece of code for my .vimrc

if has("autocmd")
  " Highlight TODO, FIXME, NOTE, etc.
  if v:version > 701
    autocmd Syntax * call matchadd('Todo',  '\W\zs\(TODO\|FIXME\|CHANGED\|XXX\|BUG\|HACK\)')
    autocmd Syntax * call matchadd('Debug', '\W\zs\(NOTE\|INFO\|IDEA\)')
  endif
endif

Basically, it allows me to define keywords which are matched with different highlighting (Todo and Debug are the names of the colors).

Is there a way that I can define my own coloring schemes and give them names? Specifically what I want to hav开发者_Python百科e is 3 tags: TODO1, TODO2 and TODO3. The idea is that TODO3 is lower priority than TODO1 and thus is highlighted in a lighter shade.

If I can't define my own coloring, where can I find a list of the color names I can use?

---

If you don't want to use default theme colors, here is the solution:

" Define autocmd for some highlighting *before* the colorscheme is loaded
augroup VimrcColors
au!
  autocmd ColorScheme * highlight ExtraWhitespace ctermbg=darkgreen guibg=#444444
  autocmd ColorScheme * highlight Tab             ctermbg=darkblue  guibg=darkblue
augroup END

And later on (this must be after):

" Load color scheme
colorscheme yourscheme

Color definitions follow the format:

autocmd ColorScheme * highlight <ColorName> ctermbg=<TerminalBackgroundColour> guibg=<GuiBackgroundColour> ctermfg=<TerminalFontColor> guifg=<GuiFontColour>

Where the cterm colors must come from a predefined list (see :help cterm-colors for more info). Gui colors can be any Hex color.