Extract all colors with Ruby from a stylesheet.

extract_colors.rb

css = IO.read('application.css')

# find all hex color values
hex = css.scan(/#([0-9a-fA-F]{6}|[0-9a-fA-F]{3})/).flatten.map(&:strip)

# convert the short code colors into long versions
hex.map! { |color| color.length == 3 ? (c = color.split('')).zip(c).join : color }

# find all rgb and rgba color values
rgb = css.scan(/(rgba?\(\d+,\s*\d+,\s*\d+(?:,\s*\d+(?:\.\d+)?)?\))/).flatten

# split rgba and rgb
rgba, rgb = rgb.partition {|value| value =~ /^rgba/ }

# convert rgb to hex
hex << rgb.map { |color|
  color.match(/[\d,\s]+/)[0].split(',').map(&:strip).map { |value|
    value.to_i.to_s(16).rjust(2, '0')
  }.join('')
}

# join colors
colors = hex.flatten.map { |color| "##{color}" } + rgba

# ensure a unique color set
colors.uniq!

# print for insertion into Sass file with generic variable names
colors.each_with_index { |color, index| puts "$color_#{index}: #{color}" }