However, a button to click would usually contain a word defining the action when clicking on the button. So does a button showing “On” mean it is already turned on, or does it mean it will turn on after you’ve clicked it?

I’m in agreement that some visual state for the button gives more UI feedback. It need not be a colour though. The Checkbox idea shows pretty clearly an On/Off state. If you want something to work for both the mind-reading-impared (Ha!) as well as the colour blind, then your best bet is not to focus so much on colour or words, but rather contrast:

I.e. give the button a different surround when on, or give it a higher contrasting backgound, or as in some apps: make the On state into a depressed look.

There’s obviously nothing stopping you from combining 2 methods to enhance the “feature” though. And IMO that’s always a better idea than to simply expect the user to know what you (as the developer) intended for  button with a particular state.

This feature evolved from a previous feature where the internal status was represented by a simple word with a colored background.

After we added that our customers wanted the ability to change the internal status after the log was created (which previous could on be set when you created it)

None of our usability tests turned out negative, when it came down to it the crux of the issue was that we couldn’t settle on the inverse language for the “off” state.

Sensitive [Insensitive] [Not Sensitive] [Unsensitive] [Safe to view] …
Internal [Not Internal] [Safe] [External] … 
Public [Private] [Not Public] …

We got a lot of positive feedback after we shipped, but I’d love to revisit this I just haven’t come up with a better alternative yet.

UI controls should not simply change the color, they should change the way it is represented.  A checkbox clearly shows something is checked.  In the case of a switch control the color helps as a visual cue, but the word should change as well.  Just like on the real lightswitch on the wall.

The iPad/iPhone switches do this, change the word from OFF to ON as well as change the color.

I find color changes by themselves confusing and I’m not color blind.  It takes a lot of experience working with the UI before you realize the developers choose orange to represent on.  When you’re neck deep in the app you don’t realize this.

I think that’s why it’s also important to do usability tests by showing screenshots to someone not familiar with the app and ask them what it means, or what they’d click if they wanted to do something.

In fact, in most cases, they are not entitled to private conversations, so that is usually the default for most of our customers.

Where the concerning employee is Burt Reynolds… I have a huge test data suite involving characters from Smokey and the Bandit