despite being an “Undertale” fictive I’m not very knowledgeable about a lot of things that are common knowledge to much of UT fandom, especially the UT fanwriting community, who have built extensively on what fragments of information about the workings of the “Undertale” universe can be gleaned from “canon”. heck...I’m not even entirely sure what “canon” is these days; there’s a lot of ancillary UT material from Fox that I’ve yet to see. what I know—imperfectly at that—is the game itself.
and in the game, there’s some mapping of human virtues onto colors of human SOUL. the virtues get named explicitly in the “Ball” minigame and they pop up in the fight with Omega Flowey. I don’t remember the catalogue off the top of my head, but I do at least remember that red SOULs have the virtue of Determination.
that might seem purely arbitrary. there’s no obvious “logical” reason why the color red should stand for “Determination”, or why any of the other colors should mean what they do. yet the symbolic association is there, and it’s not unique to “Undertale”. other fictional worlds, in various ways, both direct and indirect, map particular human virtues onto particular colors.
because I’ve been watching a lot of Super Sentai lately, I’m especially reminded of how Sentai squadrons get color assignments that tend to line up with personality types. the tropes are so reliable that they can be made fun of, cf. the Sentai parody show Kanpai Senshi After V.
Red is almost always the leader; the only exception I can think of at the moment is Kakuranger, in which Red is more like the chief lieutenant of the true leader of the squadron—the White Ranger, Tsuruhime. (but Kakuranger is a somewhat eccentric member of the Super Sentai canon.) there’s a range of personality types and leadership styles for Red Rangers, but a particularly common style is the hotheaded, impulsive Red: a go-it-alone sort of hero, who tends to think with their reflexes and their “guts” while the rest of the team rolls their eyes. but this sort of Red Ranger is respected as a leader for one big reason: they’re the most determined. over and over, they get themselves in way over their heads, and get clobbered, but they simply will not drop; again and again they stagger to their feet and win through sheer persistence and luck.
Determination, I trust, has a broader range of human expression than simple stubborn persistence. but there’s something special about heroes whose determination is that basic. and...well, it’s generally the Red Ranger who’s like that in Super Sentai. so what’s with red and determination?
~Chara of Pnictogen