Set about talking to some WS2812 addressable LEDs over the weekend and made this demo up. There's a sheet of paper in front of the LEDs to make the colors more pronounced.
The processor is a cheap STM32F401 board which sends the whole string of all 7 LED colors to its PWM timer over DMA.
Colors are advanced every 10 ms. Every 1 ms, the colors are blended by a weighted average to smooth out the effect. Overall, the LEDs look like they update at 100 Hz.