in lib/ansi2html.rb [203:216]
def get_xterm_color_class(command_stack, prefix)
return unless command_stack.length >= 2
return unless command_stack[0] == "5"
command_stack.shift()
color_index = command_stack.shift().to_i
return unless color_index >= 0
return unless color_index <= 255
get_color_class(["xterm", prefix, color_index])
end