-- transform to <span style="color: red;"></span>
if FORMAT:match 'html' then
  function Span(el)
    color = el.attributes['color']
    -- if no color attribute, return unchange
    if color == nil then return el end
    
    -- remove color attributes
    el.attributes['color'] = nil
    -- use style attribute instead
    el.attributes['style'] = 'color: ' .. color .. ';'
    -- return full span element
    return el
  end
end