Grixis
So, it's taken me a very long time to understand what grixis truly is. I am grixis myself. It took a long time, given my own history of trauma to understand what was maladaptive psychology from that, what was the shadow rearing it's head and what was maturation across the lifespan.
So with grixis I started out as a typical izzet, full of creativity and a thousand ideas a second, your typical creativity for creatives sake enjoyer. Due to trauma I alternated between the extremes of both blue and red more heavily than the normal person. Exreme impulsivity and thrill seeking vs extreme coldness and intellectualisation.
At a certain point as an mbti entp (as I am, though I am certain grixis can present elsewhere), you end up sick of theories that lead nowhere and impulsivity that suppresses your natural strategic inclination. I believe izzet to grixis is one of the most common entp paths. This I think is where the real shadow integration occurs and the development towards black comes into play. This is when you stop being the bad internet stereotype of entp and move from trolling and wasting energy everywhere to a more refined, emotionally and intellectually selective mindset, only engaging with things that give you meaning or value. Sounds cold but it's not really, it's strategic. Conservation of resources.
Thing is is then you can end up in the black shadow integration too heavily, this is where concepts resembling Laveys satanism can kind of take you over and you can get stuck there if you make the wrong move and take the short term view. Laveys satanism is literally grixis distilled. Issue is is it becomes an excuse for self inflation and callousness and god help you if you start diluting yourself by taking actions against your natural moral inclinations as this will permanently lower you in your own eyes. I managed to avoid that fortunately.
The truth of it is that although grixis has a tendency towards selfishness or moral certitude, that it's actually just the black part forming late and the shadow gaining sway, unless you take enough actions that dilute you, your ego will end up in check soon enough. Edgelordism does not tend to survive until middle age unless you have done enough to force your ego into a defensive position it can't dig it's way out of. The counter is shadow integration and being honest about yourself, you will be forced to if you have any conscience personally and self awareness, better to face yourself on your own terms.
I believe grixis to be three wildly differing personality structures combined that take a lot of time to integrate healthily. I believe there is nothing inherently bad or negative about grixis but it has potential towards three extremes that are highly maladaptive. I believe grxis becomes it's strongest when it integrates it's ego and darker impulses fully and then it becomes a very specific form of powerful.
The traits that give it away are a crazy quickness in thinking, izzet core. Extreme selectivism in how it's energies are used, not performative signalling, dimir core. Emotional intensity applied in selective places, with trusted friends, rakdos core.
Grixis people are usually quite intelligent, extremely adaptable. Intense in a way people feel in their bones. Quick witted and capable of charm, highly strategic when not ruled by their shadow. May not suffer fools very well and above all, absurdly determined and willful.
Grixis is forged in the fire of it's own disparate personality structure, it can look awful in youth, but fully integrated? Terrifyingly effective and just feels different and outside the norm. It's the kind of person you find yourself thinking you have romantic chemistry with because their baseline presence is so intense but then looks confused when you clarify that you are in a relationship. Grixis is not hard to spot if you know what you are looking for.