Blood Type (also referred to as Pattern) is a measurement of wavelength pattern used to determine the nature of a particular being. The nature of the wavelength pattern in question is currently indeterminate, as is the reason for its diagnostic power.
Following the berserk Evangelion Unit-03's analysis, a picture of something matching the structure of hemoglobin (the oxygen-carrier protein in blood) appears on the monitor. The Magi appear to factor in genetic pattern while calculating the reawakened Lilith's blood type. Despite the name and hemoglobin allusion, there is no concrete indication that "blood type" has anything to do with physical blood.
Blood Type Blue (パターン青, pata-n ao) indicates that an entity is unambiguously an Angel.
- Kaworu Nagisa falls under this despite having a Lilin component.
- After Lilith absorbs Rei and Adam and reawakens, the Magi catalog her as Blood Type Blue. It is unknown if Lilith would have qualified as "Blue" before fusing with Adam.
- In Rebuild, subtypes of Blood Type Blue exist, and Unit-01 is shown as belonging to one of these from the start.
- While under construction, tubing going to and from Mark.06's left arm is attached to a container marked "BTB". The most intuitive breakdown of the acronym is "Blood Type Blue".
The Angels' Blood Type Blue is a reference to the Japanese SF film Blue Christmas. In the film, UFOs buzz the Earth and the innocent witnesses all suddenly have blue blood, with the result that society and the government hunt them down and exterminate them. The protagonist is ordered to exterminate his blue-blooded girlfriend.
The protagonist may be analogous to Shinji killing Kaworu. More generally, the blue-bloods are—apparently—harmless and their purge demonstrates the evil in the hearts of men. Similarly, the Angels traveling to Tokyo-3 rarely initiate combat or attempt to kill humans out of cold blood, while the conduct of the humans themselves is ethically questionable.
Blood Type Orange (パターンオレンジ, pata-n orenji) typically denotes some form of ambiguity over an entity's identity or form. It is used to designate:
- Leliel's shadow, before the ultra-thin body appears
- The contaminated Evangelion Unit-03.
- Armisael while in its initial ring form. It fluctuates between blue and orange, which Ritsuko interprets as meaning that the Angel is polymorphous.
Pattern Red (パターンレッド, pata-n reddo) is what Evangelion Unit-01 shifts to moments before merging with the Spear of Longinus and forming the Tree of Life. It is unclear what the change denotes. According to Fuyutsuki, Unit-01—as a being with both Fruits—has been "restored" to "embryonic" Tree of Life form.
Green is mentioned during the pilot cross-compatibility test in Episode 14.
- Neon Genesis Evangelion Platinum Booklet Commentaries.