I am now 18 years old, but I had a lot of sleepovers when I was growing up.  One of the best ones I had was my moms idea.  It was called the "Purple Party" since purple was my favorite color. (Can be used with any color of course) The invitations were on purple paper and directed everyone to wear something purple to the party.  The plates, cups, napkins, cake, etc. were all shades of purple, mostly a bright shade.  We served other foods such as grapes, grape koolaid, purple tortilla chips and salsa, and purple popcorn. Most of the guests caught on early and my gifts were purple. All of the decorations were purple and we danced to the Purple People Eater. All of the goodies given to our guests were purple and everyone took home a giant purple balloon.