added Function coloring

[shmerl]

I used violet color, as per suggestion to use existing colors, but personally, I don't like the way it looks in result. I'd prefer a more contrasting color, as in my example. Something like:

let s:colors.sea   = { 'gui': '#4d618e', 'cterm': 4  }
...
" Function.
call s:Col('Function', 'sea')

[whatyouhide]

Awesome, thanks a lot @shmerl! 💟