This is what I found when I did a search
So here's a few easy steps to achieve the goal of "going dark". I (currently) have 2 methods to doing this:Be careful - remember you need to be able to set it back to it's original colorations after Monday.
Turning your page black, i.e. make the backgrounds, text etc. black. Yes, I'm taking it literally here, but you're blog is going to be completely blank. An example can be seen here ( http://robtestblog1.blogspot.com ).
If you need details, you click "Design" in your dashboard.
Then, above your blog layout there's a tab that says "Template Designer".
In this go to Advanced and change every colour to black (#000000).
If you post videos or pictures with your text, I would advise setting number of posts on front page to 0.
This can be done by going to settings, then formatting and it's the first option.
Method 2: This, I think, is closer to going dark than the previous method, but not perfect. It also happens to be much easier, so bonus!
Go to Settings again, but instead go to permissions from here (it's in the same taskbar as publishing).
Under Blog Readers select "Only Blog Authors".
This means only you (and any other people you have given permission to be authors on the blog) can see it. When people try to visit your website, they will not be able to view it, thus, going dark!
I hope this was helpful, and if any of you true Blogger boffins out there know a better way to do it (maybe the proper way) post a comment below wherever this was copy-pasta'd to. Yours Faithfully, Rob CircleGuy http://twitter.com/theCircleGuy