Hidden State Colors

I've got something interesting happening somewhat inconsistently when I change the state of an image or group of images to hidden and then change it back to normal.

Usually what happens is that, when the item is hidden, it changes to greyscale in the slide creation window.  

If you change it back to normal, usually it goes back to its original color.

However, I've noticed that sometimes, it does not:

Here is an example of what I'm talking about:

http://screencast.com/t/WiGTuSHXvstI

As you can see the image is set to normal, and there are no triggers that could cause it to be greyscale.  The normal mode state shows the image in color.

When you preview the slide, the image is in color: 

http://screencast.com/t/GM7hWZMWNx

The rest of the images in this same slide were initially all in the hidden state as well, but they all went back to being color when I changed them back to normal, all except this one for some reason...

Is there a setting I'm missing somewhere, or is this a bug with the software?

Thanks!

-Martin