Here's the MS SQL docu pages http://msdn.microsoft.com/en-us/sqlserver/aa336270 (but they change their design every few years. A couple years back it was a blueish theme, now they've gone predominantly grey)
Here's the Oracle docu pages http://www.oracle.com/technetwork/database/enterprise-edition/overview/index.html (Also grey)
Here's the MySQL docu pages http://dev.mysql.com/doc/refman/5.5/en/ blue and orange this time.
The NoSQL guys really don't have a centralized theme on account of that's like saying "flowers" and lumping in everything from roses to daisies to orchids, etc.
The above are the "big three" that most people have to support, but I figure you knew that. This is just some thoughts on what sort of coloration to go for.
For the codeblocks, I would love to suggest something with a colored stripe on the left hand side, with marginally smaller fonts on the fixed width format. idk if this is easily doable, but just an idea.
I'm drawn to using an orange (a-la the MySQL docu pages) for that left hand margin.
Since the meta will already be grey, I think limiting the amount of gray on the main will be a good idea. So blues become the primary hue, I think. Not altogether unlike sketchy.
However, these are just thoughts. I'm no graphic designer. I stand back and wait to be amazed ;)