I think your question is more about the furniture than the room colors- I believe you will find what you are looking for in a Captains bed. It sits higher off the floor and can accomodate a great deal of storage. Load it with pillows for sitting on with your friends. You can still use lower seats on casters in front of the bed as you suggested without an odd appearance.
Try this for the beds: http://www.shopping.com/xFS?KW=captains+bed&CLT=SCH
I do suggest you search for captains beds at various sites to find exactly what you want. You can also look for Captains beds plans (to buid it yourself) Bed risers will also lift the bed, just find storage that complements your room for beneath the bed. I suggest seats on casters example: or on rockers like this: http://www.target.com/Rocking-Floor-Seat-Collection/dp/B000REMVFG/sr=1-1/qid=1215464462/ref=sr_1_1/602-2648974-9875862?ie=UTF8&index=target&rh=k%3Avideo%20seats&page=1
I know it is not a sofa but get 2 or 3 to place in front of the raised bed and you will have plenty of room for your friends.
this one is also great to extend seating space even more! http://www.target.com/Couch-with-Ottomans-Black/dp/B000K1QO5O/qid=1215464533/ref=br_1_4/602-2648974-9875862?ie=UTF8&node=13299851&frombrowse=1&rh=&page=1
Keep the color bright and use the walls for storage as much as possible. Go Verical for storage. Use wall mounted bins, DVD racks, marker board or cork board. Grab a lap tray for instant desk anywhere. for fun see: http://www.target.com/Unforgettable-Doorganizer-Collection/dp/B000F0FXRA/sr=1-11/qid=1215464819/ref=sr_1_11/602-2648974-9875862?ie=UTF8&index=target&field-browse=1038614&rh=k%3Acollege&page=1
http://www.target.com/Over-the-Door-Organizer-Black/dp/B0019S20CS/sr=1-2/qid=1215464948/ref=sr_1_2/602-2648974-9875862?ie=UTF8&index=target&field-browse=3665671&rh=k%3Acollege&page=1
http://www.target.com/Over-Door-Purse-Storage-Rack/dp/B000NBV9CO/sr=1-1/qid=1215465047/ref=sr_1_1/602-2648974-9875862?ie=UTF8&pricerange=&index=target&field-browse=3665671&rh=k%3Acollege&page=2
If you're willing to do some work, grap some paint and check out Ikea for other storage units. Get creative, think of new ways to use what you have and make it unique for you.
Michele