Modern brides have grown quite a liking towards colored gemstones in recent times too.
Allochromatic gemstones are those, which are typically colorless but appear colored due to the presence of subtle impurities. For instance, the pure conundrum is colorless, but due to the presence of traits of chromium, it is typically identified by the color red. Similarly, it appears blue when the stone has a presence of titanium. The former is called ruby while the latter is commonly known as a sapphire.
A few more examples of Allochromatic gemstones are beryl, tourmaline, nephrite jade, topaz, and spinel. Some of these gemstones are also found in their pure state but are of low value; this category includes quartz, corundum, topaz, and beryl. On the other hand, the pure form is extremely rare in some gemstones, and hence, they are very precious. Examples of this category include nephrite jade, tourmaline, and grossular garnet.
Note that some of the Allochromatic gems do not have colorless variants in nature, such as spinel. However, you can still get hands-on a colorless spinel engagement ring that features a lab-created gemstone.