Create new command and set scope selector to `source.css` and semantic class to `callback.document.did-open, callback.document.did-save`

CSS Colors in Gutter.rb

#!/usr/bin/env ruby -wU
require 'erb'
require 'fileutils'
require 'shellwords'

# extension to String to extract colours into rgb array
class String
  # hex to array
  def h2a
    if self.length == 4
      self.scan(/[0-9A-Fa-f]/).
      map {|i| (i*2).to_i(16) }
    else
      self.scan(/[0-9A-Fa-f]{2}/).
      map {|i| i.to_i(16) }
    end
  end
  # rgb to array
  def rgb2a
    self.gsub(/[\s\(\)rgba]/,'').
    split(',')[0,3].
    map{|c| c.to_i}
  end
end

# extension to Array to divide all elements by 255
# to get decimal rgb value
class Array
  def by255
    self.map{|i| (i/255.0).round(4).to_s }
  end
end

# template for 
def get_template()

end

class ColorBox

  include ERB::Util

  attr_accessor :color, :dir

  Template = %{
%!PS-Adobe-3.0 EPSF-3.0
%%BoundingBox: 0 0 80 80
gsave 0 0 80 80 rectclip gsave
<%= @color.join(' ') %> setrgbcolor
10 10 70 70 rectfill
grestore grestore
}

  def initialize(dir)
    Dir.mkdir(dir, 0700) unless Dir.exist?(dir)
    @dir = dir
  end

  # set color
  def set_color(color)
    @color = get_rgb_array(color)
  end

  # get array from color string
  def get_rgb_array(c)
    if c[0] == '#'
      return c.h2a.by255
    end
    if c.match(/^rgb/)
      return c.rgb2a.by255
    end
  end

  # render the template
  def render()
    ERB.new(Template).result(binding)
  end

  # save the file in the given dir unless it exists
  def save()
    file = File.join(@dir, @color.join('-')+'.eps')
    unless File.exists?(file.to_s)
      File.open(file, "w+") do |f|
        f.write(render)
      end
    end
    return file.to_s
  end
end

def markup 
  dir = "#{ENV['HOME']}/Library/Caches/com.macromates.textmate.colors/"
  args = [ "--clear-mark=#{dir.shellescape}", "--uuid=#{ENV['TM_DOCUMENT_UUID']}" ]
  box = ColorBox.new(dir)
  ARGF.each_with_index do |line, idx|
    line.scan(/(#([0-9A-Fa-f]{3}|[0-9A-Fa-f]{6})(?=[^0-9A-Fa-f])|rgba{0,1}\([0-9]{1,3}[, ]+?[0-9]{1,3}[, ]+?[0-9]{1,3}[, 0-9\.]*?\))/) { |c|
      box.set_color(c[0])
      args << "--line=#{idx+1}" << "--set-mark=#{box.save.shellescape}"
    }
  end
  system(ENV['TM_MATE'], *args)
end

# fork and redirect output to log
pid = fork do
  FileUtils.mkdir_p("#{ENV['HOME']}/Library/Caches/com.macromates.textmate.colors")

  STDOUT.reopen(open("#{ENV['HOME']}/Library/Caches/com.macromates.textmate.colors/log.txt", 'w'))
  STDERR.reopen(open("#{ENV['HOME']}/Library/Caches/com.macromates.textmate.colors/err.txt", 'w'))
  markup
end
Process.detach(pid)