I would want to know what the custom is in your kid's school. My kid's high school friends spread the parties out over the whole summer because there were so many, and kids had different social circles so not all kids attended the same ones. So, chances are your party date/time will conflicts with about 10 others, so be aware of the conflicts.
I don't think kids care as much about themes as some parents do. If you spend a fortune and the kids just roam in and roam out, and your daughter heads out after an hour to someone else's house because "all my friends are going," how will you feel? And if you go way over the top with a badass entertainment blowout, you may attract kids who aren't even her friends. Then the guest list swells and you can't control it. All you need is 4 kids sneaking beer and vodka into a big crowd, getting in a car drunk, and having a tragedy. We've had a few instances in surrounding towns where large and uncontrolled parties end in a pretty bad situation, including vandalism, property damage, and parents brought up on liquor charges, so be careful to define what "badass" means and how it filters out beyond your daughter's immediate social circle.
We had a party in our back yard, and my son hooked up some outdoor speakers to blast their music. We had the usual party foods, some kids brought a corn hole game, and the kids threw frisbees around the back yard. They had a blast. Other families had a party around a pool if they had one or were in a neighborhood association that let them reserve the pool and patio area, others did a BBQ in the park. I don't know if these qualified as badass parties but the kids had fun at all of them.
I would get a few ideas and ask your daughter what she wants, but it may be that you will just be a few weeks away before she decides (after she hears what others are doing).
We found that it was not the custom to give gifts because it would have been families basically trading cash - "I give your kid $25, you give my kid $25. Lather Rinse Repeat." There were some gifts from relatives but, honestly, the graduating kid didn't have as much time to spend with them because there was a house full of friends too.
College colors are fine - we did that with tablecloths and napkins etc. Remember that not all her friends are going to college so be careful you aren't rubbing anything in. In our town, people often have banners made that say "Congrats, Jillian, Class of ___" or they use bedsheets and fabric paint, and hang them out the 2nd story windows, but it's not everyone. And our local police remind people who advertise that they have a graduating senior to have someone watch the house during the grad ceremony, because families have just advertised, "We're not home."