Graduation parties are held to celebrate formal occasions, but are usually held in more casual atmospheres. Therefore, the appropriate graduation party attire depends on where and when the party is being hosted. A party at a nice restaurant or indoors at night will call for more formal attire, while at outdoor party during the day or on a weekend will require less formal clothing.
For parties on the less formal side (outside, during the summer, during the day, barbeques), less formal clothing is required. You still want to make a a good impression and look appropriate, so a nice pair of pants and colored shirt is appropriate. Chinos and Khakis work well here. For more formal occasions (such as dinners or parties at a restaurant), more formal attire is appropriate. This includes darker wool pants and darker shoes.
Dress code depends on the location, time and season
Many parties are outdoors - dress in lighter colors for these
Looking good is important, but also don?t forget to bring a gift!