IMG Hover over fade not working.

I’m trying to add this effect to some images on my WordPress site. ( The first effect, Grayscale To Color CSS )

http://www.mountainmarketingsolutions.com/css-image-hover-effects/

I’m using a pretty hacked version of Themify Base. But I have tried installing other themes that I haven’t messed with as much to see if it was something I did. The effect still doesn’t seem to be working. I also tried adding the CSS locally on the page I want it on. Still didn’t work. I’m sure it’s something I’m not doing correctly because I’m no developer. But I’m copying and pasting the code so it’s exact to what this guy is using. Anyway, if anyone has any ideas that would be great.

Thanks