This is a RGB LED light-up dress I made for my niece for Halloween 2016 as she wanted to be a princess and I wanted to make her something magical. Nearly everyone who saw it while trick-or-treating had a reaction to it.
I used 5050 RGB LED strips, a simple 12VDC regulator, and Ryobi 18V cordless tools lithium ion battery to make the LED dress.
The 5050 RGB LED strips are mounted to a peiticoat / underskirt to allow the dress to be washed, modular, and to "poof" out the dress for extra effect. The LEDs are mounted facing inward to make a diffused glow and so the dress will not have point light sources.
For the power regular I used a super overkill cheap 240W step down buck power supply I found on amazon. I wanted something fully enclosed, waterproof, low heat, for piece of mind against arcing or overheating. There is probably a much better potted or fully enclosed low cost solution out there and would like to see what others recommend. There are a ton of low cost buck regulators on ebay but I have not seen good options for ones that are potted.