Meet the Musixel: a cool kit that add lights to your music. Just attach a music source and the Musixel will convert the frequencies into colors. It mixes colors upon detecting multiple frequencies. The kit comes with a LED strip with 9 different color modes. You can expand it to 64 LEDs.
The Musixel comes pre-assembled and does not require soldering to work. You get audio cables, an audio splitter, an adapter, and everything you need to get started. The kit is available for under $35.