Blue Monday is an awesome "blue themed" map pack from some of the best Quake mappers in the community.
Bear in mind this map pack requires the Quoth mod which you can find over on Quaddicted as well.
To set up Quoth, in your quake directory, make a sub-directory and name it quoth (follow my full QuakeSpasm setup guide here). Extract the contents of the Quoth zip here.
To load Blue Monday, firstly extract the contents of the downloaded Blue Monday zip file into a new folder in your quake directory called bluemonday. Run QuakeSpasm and then press "Esc" to load the Quake command prompt. Now type:
game bluemonday -quoth
Press "Esc, select New Game and you're off to the races!