A 45 year old a kit from Dick Smith Electronics.
I built it when I was at school.
From Electronics Australia September 1976.
From the Assembly Manual.
The Musicolor 3 kit from Electronics Australia magazine will turn your music into an exciting kaleidoscope of vibrant color. Easy to use: simply connects to the speaker terminals of any amplifier (stereo, mono, guitar, cassette, etc) and uses music to control 3 channels of colored lights. Ideal for Paraflood or any other incandescent bulbs. Completely safe will not harm your amplifier or your music in any way.