def rainbow(str)
    i=0
    ret = '' 
    str=str.to_s
    while(i < str.length)
      ch = str[i]
      palette = $color_db[0][i % $color_db[0].length ]
      ret << (colora(palette,str[i,1]))
      i += 1
    end
    ret
  end
def rainbow(str)
    i=0
    ret = '' 
    str=str.to_s
    while(i < str.length)
      ch = str[i]
      palette = $color_db[0][i % $color_db[0].length ]
      ret << (colora(palette,str[i,1]))
      i += 1
    end
    ret
  end
carattere per carattere...