Why violet glass and not amber, green, or clear

Light is what degrades what you are storing. Terpenes oxidise and THC converts to CBN, and the blue and green wavelengths do most of that work. Clear glass stops none of it. Green glass stops some. Amber stops more but still passes visible light.

Violet glass blocks effectively all visible light, roughly 380 to 780 nanometres, while letting UV-A and infrared through. That is the whole reason the glass is this colour, and it is why pharmacies used dark glass long before anyone was storing concentrate in it.

Ours is true ultraviolet glass all the way through, not clear glass with a coloured coating sprayed on the outside. A painted jar scratches, chips, and stops protecting anything. We use these jars ourselves in Humboldt County and they are what local processors here buy.