It's interesting to discuss the color schemes of people's clothes or even their skin or hair. The Red Haired pirates, for example, might not just have that name for aesthetic qualities (beauty). But, it might have a more meaningful title if it's going to indicate something about the type of pirates they are. Where it concerns all the Pirate Emperors, I think they may possess more encompassing ability schemes than other characters. Thus, they have dominance over them as they can deal with a multitude of combat situations where others simply may not. Whether their set of abilities is based on Devil Fruits, Haki, or any other form of offensive or defensive capability. Kaido, Animate Scheme (natural tools to overcome obstacles). [Beasts]. Big Mom, Inanimate Scheme (unnatural tools to overcome obstacles). [Objects]. Shanks, Primal Energy Scheme. [Vital Life Force]. When speaking of their own ability scheme, consider their underlings schemes as well. It may be important to note that they often use the underlings to make up for abilities they themselves do not possess (all of Big Mom's animated objects may be considered underlings for example). But, where it concerns the Red Haired pirates.. I think many of those guys have Strong Wills. This might be indicative of Berserker style tactics due to the correlation that can be made with the same energy which can be related to Oars giant red body. Oars might be an example of what happens when a living organism continues to absorb that type of energy for... who knows how long, there's probably generations involved and he was probably a freak amongst freaks (an incredibly rare sight). Then... I also remember hearing about a Giant Red Sea Serpent that might show up at some point. That, too, may have something to do with that. Though, much of this is simply speculation. In any case, where it concerns the Red Hairs~~ the red hair itself might be indicative of a vital life force, Shanks has also been described as someone who "really knows how to live" (he partied when everyone he was around was on the mend). Then, we see someone recruited to the crew at some point who has spikey red hair and rode in on a surfboard like Ace does. --- Often times, when thinking about color schemes and their relationship with colored energy~~ it will be difficult to accurately measure how the developments occur. But, they are definitely interesting to consider and some of them will seem certain. Others, less so. But, they usually explain themselves quite easily if the message is clearly understood. --- You talked about White for a moment there. I'd like to give my thoughts on that as well. White and Black are actually.... rather important. I didn't want to talk about them alongside the basic seven colors right away because Light Red and Dark Red might be two different things. White and Black... and Light... are all part of the same thing. Without light, there is no color; darkness (black). Philosophically, light and darkness represent the Creator and the Destroyer. So, if a King were to use his Red energy destructively~~ it would be the act of a Destroyer; a Darkness ability. That is to say, a Divine application (Crown Chakra) using Red Energy (Root Chakra). The King Haki, itself, might not be shown to be mixed~~ violet and red. Instead, it might be Red tinted Black. This has been seen in several abilities (like the King's Punch). But, as I said... sometimes it's not so clear when trying to determine these things. Even though there is a level of certainty. Here's something that might throw you on a loop, Armament Haki is Black. It's also used for combat purposes (so it has reasons for being black). But as I said... Black occurs when no light is present. That's not entirely true. Light can be there. But, sometimes, there's so much color that it gets combined and turns into black due to compounding saturation and color density. Levels of color saturation and hue. Then, too, auras themselves are [projections] of the inner energy (Haki/chakra). This causes certain changes to occur. For example, the aura might only be green~~ but, the person themselves might have many other colors involved in their inner chakra. Green is just the one being shown outside of the body at that time.