Without a doubt, Persona fans are eating good with Atlus recently acknowledging the development of Persona 6 and challenge of surpassing Persona 5. They even know more official news regarding the franchise's anniversary will be taking place in September, and a proper Persona 6 reveal may very well happen then. That's not a long wait, but that hasn't stopped fans from looking into everything Atlus has done recently for clues.
Including the Persona anniversary design, there are quite a few clues as to the next protagonist. Piecing those together could be indicative of a few details regarding the Persona 6 protagonist, though until any official confirmation, this is simple speculation.
Piecing Together the Persona 6 Protagonist
First, as many have pointed out, the above image may hint at the primary color of Persona 6 being white. Every game has featured a primary color of sorts, with Persona 5's being red, and Persona 5's color was teased in a similar manner before its reveal. Essentially, looking at the "Persona 25th anniversary" logo, each color from the above games are highlighted alongside white—which doesn't really pair with any other game.
On top of that, there are a few known details about Atlus' approach to character design. First off, the last two Persona protagonists were designed with animals in mind. Joker's inspiration from a black cat makes sense, as he is lanky with unassuming characteristics, and he tends to blend in well. It's easy enough to see from an inspiration point of view when looking at Joker, and the same could be said of Persona 4's Yu Narukami, who was inspired by man's best friend, a dog.
Lastly, another key point is that Persona protagonists are often associated with the Fool Arcana. As "number zero," it is from which all begins and represents innocence, divine inspiration, madness, freedom, spontaneity, inexperience, chaos, and creativity, with Personas derived from it typically being a "Jack of All Trades." And protagonists of Persona 3 and Persona 3 Portable, Persona 4, and Persona 5 are all somehow tied to the Fool Arcana. There's also sometimes the concept of the Journey of the Fool at play, where the Persona 3 and Persona 4 protagonists are given a Persona of Judgement/The World at the end of teh game.
Persona 6 Protagonist Elements
As such, while there is obviously margin for error, fans can expect a protagonist who is surrounded by white color schemes, or may in and of themselves be associated with a certain innocence. Perhaps that white also connects to their animal inspiration design, as birds (fish too) are the most common pets alongside cats and dogs. A cockatoo, a commonly white bird, could serve as a "caged being wanting freedom" style of inspiration, while perhaps also suggesting a more wild hair style. Or, what's more likely, the color association and animal inspiration are divided. Still, if Persona 6 follows this approach to design, then the aforementioned animals are the most likely inspirations for their design.
Finally, at least at the start of the game, fans know the Persona 6 protagonist will likely be associated with the Fool Arcana. None of this obviously fills in the blanks of their character design or of any gameplay elements, but whenever they are properly revealed, fans should pay attention to all the small details like these.
Persona 6 is in development.