The flame (炎,honō?) of a certain being, especially of a Crimson Denizen, is a physical manifestation of that being's Power of Existence, and is not usually connected to the original meaning of "flame". It is usually in a fire-like form, except for other special cases, thus the term used.
A Crimson Denizen's flame has a distinct color, and is usually seen when they manifest in the living world or when they acquire injuries; instead of blood, "flames" made out of Power of Existence shoot out from their wounds.
Distinguishing what color of flame one possesses is based on ambiguous interpretation via Tatsui no Gen. Basically, there are no Crimson Denizens who share the exact same color of flame. However, after one's death, it is up to Tatsui no Gen's interpretation whether the same name of that color will reappear.[1] There are currently two examples of when Crimson Denizens have the same name of flame color: Khamsin's nemesis the Monster and Rofocale; Thrym and Guita.
There is only one unique case: the AizenSiblings who, in truth, are divided roots from one individual that still intertwined with each other; thus, they share the same color of flame.
Rinne, or servants created by Crimson Lords or Denizens, usually adopt the color of flame of their maker. For example, Marianne, Friagne's Rinne, also has his color of flame, pale white. Meanwhile, Flame Haze also adopt the color of flame from a Crimson Lord which, in this case, is the one with whom the contract is bound with.
Torches can also manifest a flame made out of Power of Existence, and this usually comes from the Crimson Denizen which has devoured that Torch's Power of Existence. The color of the flame, however, cannot be determined. There are some cases, however, that the source of the Power of Existence used to create a Torch can be determined, as a person's body can be compared to a lamp with a flame inside.
This table lists down the different colors of flame manifested by a certain Crimson Denizen or Lord. It is listed according to color range and gives out the name of the Denizen, the actual color, and the description of that color. In the second column, the color will be given as the background while the RGB code for that color is given. All RGB codes are sourced from colordic unless stated otherwise.