The Inverted Paranorma texture pack swaps every color with its opposite. And as a result, as you probably could guess, it makes all of the game graphics look entirely different and a little crazy. It's harder to say whether it brings any benefits to the game as it's all a matter of color preferences but it definitely turns into something entirely unique.
Note from the creator (Cheete): Now, there is a bug with the side of the grass that I have no knowledge on how to fix so try to ignore it. Also since Minecraft doesn't provide endermen, spider, snowman, and sheep textures, they will look the same.