Blackle saves energy because the screen is predominantly black. "Image displayed is primarily a function of the user's color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen.
I know what you're thinking, I had the same thought too "The Modern Dictator is being copied again". First Ewan McGregor steals my thunder and now some dudes create Blackle obviously after having visited my black-coloured blog.
Also, have you heard about The Annoying Orange? Of course not, I am the one telling you about it. It's about an orange that's annoying...well the title pretty much gives it away. Enjoy:
And in the same vibe of The Annoying Orange:
Check it out on Youtube, there are many others.