Rockpool Colours in Natural Tibetan Turquoise, from the old mines of West Tibet, the ovals cut side by side from the same segment of mother rock, virtually perfectly matched. (Note: the Rockpool Colours of the above pair are in reality lighter than captured in the above images; certain colours are problematical for this amateur photographer: blues and greens, and dark blues such as in Lapis Lazuli, can pose difficulties.)
Most Turquoise these days is treated, by colour enhancement and stabilization, for Turquoise is an unstable gemstone, being porous and susceptible to adverse effects on exposure to, e.g., the chemicals in products such as perfumes and detergents etc, which can lead to splotching of colour.
All natural Turquoise will naturally darken a little over time and with wear. However, natural Turquoise such as the above, if treated with a modicum of care and not sprayed with perfume or doused in sun-tan lotions, will wear nicely, gradually, and will retain the original charm of its colour composition.