exceprt from an interesting read- here is link for whole article:
http://www.gardenscure.com/420/harvesting-drying-storage/83247-trichomes-process-turning-amber.html
“ Returning to the more orthodox version of the cannabinoid biosynthesis, the role of ultraviolet light should be reemphasized. It seems apparent that ultraviolet light, normally supplied in abundance by sunlight, takes part in the conversion of CBD acid to THC acids. Therefore, the lack *Carlton Thrner 1979: personal communication. of ultraviolet light in indoor growing situations could account for the limited psychoactivity of Cannabis grown under artificial lights. Light energy has been collected and utilized by the plant in a long series of reactions resulting in the formation of THC acids. Farther along the pathway begins the formation of degradation products not metabolically produced by the living plant. These cannabinoid acids are formed through the progressive degradation of THC acids to CBN acid (cannabinolic acid) and other cannabinoid acids. The degradation is accomplished primarily by heat and light and is not enzymatically controlled by the plant. CBN is also suspected of synergistic modification of the psychoactivity of the primary cannabinoids, THCs. The cannabinoid balance between CBC, CBD, THC, and CBN is determined by genetics and maturation. THC production is an ongoing process as long as the glandular trichome remains active. Variations in the level of THC in the same trichome as it matures are the result of THC acid being broken down to CBN acid while CBD acid is being converted to THC acid. If the rate of THC biosynthesis exceeds the rate of THC breakdown, the THC level in the trichome rises; if the breakdown rate is faster than the rate of biosynthesis, the THC level drops. Clear or slightly amber transparent resin is a sign that the glandular trichome is still active. As soon as resin secretion begins to slow, the resins will usually polymerize and harden. During the late floral stages the resin tends to darken to a transparent amber color. If it begins to deteriorate, it first turns translucent and then opaque brown or white. Near-freezing temperatures during maturation will often result in opaque white resins. During active secretion, THC acids are constantly being formed from CBD acid and breaking down into CBN acid. “
If I was going to break all this down into a few sentences it would read like this:
The resin gland produces cannabinoids that are converted into THC. During the active cycle of cannabinoid production the glands will appear clear or cloudy. As the plant matures and the production cycle slows the glands will change color to amber. This is caused from environmental influences, tempeture and light. The major influence on the amber color would be the lack of conversion from cannabinoids CBD and CBN into THC. You can draw your own conclusions as to why, my theroy is as the plant matures it slows in cannabinoid production and the UVB radition has less cannabinoids to convert and starts to degrade the resin - hense the color change.