You should add a section where if the input is false (etc. a door says "You need the password to enter here" and you say purple instead of blue) you can display a message (such as "I have no time for guessing games, get out!"). This is definitely a needed feature.
I also just thought that already with what you have if you can incorporate multiple actions based on one message, writing /help could result in a fire set on you and the message "There is no help for you here" displayed.
Not only do i see the potential for the command itself being added, but what other fun things they'll add alongside it. For example, only Administrators being able to have command blocks respond to whatever text they execute in the chat.