Red, orange and yellow crystals are low-grade, the cheapest and most common. They typically crumble after being consumed. They have a limited number of uses as mediums for Warden Magic and Alchemy and are useless to Forgemasters. They do not recharge by themselves.
Red crystals are considered to be "dumb" since anyone can use them, even if they're imprinted. Red crystals can prolong the duration of an array (by being placed inside the formation, boosting its mana reserve) or grant control of it to someone other than the caster (by the array caster imprinting the crystal while conjuring the array so whoever holds it can turn it on/off)
Orange and yellow crystals work the same way but have much more mana and can be imprinted multiple times, but only with the consent of the original caster.
Green and cyan crystals are middle-grade. They have much more mana and are able to recharge over time as long as they hold even a speck of energy. The length of the recharging process depends on the size and purity of the crystal, and the purer crystals take longer to recharge (the brighter the crystal, the purer it is). With middle-grade crystals, Wardens can make semi-permanent arrays if they are powered by a sufficient number of recharging crystals, though the more damage the array takes, the more mana is consumed. Forgemasters can embed them into their creations, allowing them to receive multiple powerful enchantments as well as gain their own mana capacity, which enables the wielder to cast spells they don't know or wouldn't be able to cast normally.
Most inorganic matter crumbles when infused with too much magical energy. Only mana crystals can harness this power, even recharging themselves faster using the conflicting energies deriving from multiple spells.
Blue and purple crystals are high-grade. In comparison to the lesser grades, high-grade crystals recharge at a much greater speed and can also be manually recharged. Only blue crystals and above can sustain complex functions like projecting holograms, copying documents, etc.
This is why Communication Amulets are so expensive and have at least a blue gemstone. Only the best Wardens and Forgemasters can afford high-grade crystals. Purple mana crystals have the natural ability to absorb world energy. However, high quality crystals require not only an abundant mana source, but also a lot of time to properly develop.
The mana flow of high tier crystals is called Mana Breath, which is a result of them being able to replenish their mana quickly compared to mid tier crystals.
White crystals are a tier on their own, and are never seen outside of the Royal Palace or powerful artifacts. They are the most powerful gemstones a Forgemaster can use and are capable of replenishing their energy reserves almost instantly, no matter how many times they are used. Additionally, powerful Forgemasters can enhance white crystals with a certain element. When a white crystal is cut, the world energy its compressed to its utmost limit and can be used to accelerate the growth of surrounding crystals and help them absorb world energy more easily. Despite looking like an Awakened mana core to Invigoration, white crystals don't have any life force or consciousness. The nature of the white crystal focuses the world energy, giving it a spherical form.
White crystals cannot be imprinted, which makes them harder to manipulate, just like high tiered enchantments. If given a power core, manipulating it is child's play in comparison.