The blue pentagon (Japanese: 青い五角形のマーク blue pentagon mark) is an origin mark that Pokémon obtained in the Generation VI games have. Pokémon that were hatched, caught, or received as a gift in a Generation VI game have the blue pentagon.
Prior to the release of Pokémon Omega Ruby and Alpha Sapphire, having a blue pentagon was referred to as being Kalos nativenWhile the blue pentagon is blue in the Generation VI games and Pokémon Bank, it is black in the Generation VII and VIII games as well as Pokémon HOME.
All of the first 721 Pokémon can have the blue pentagon, as each of them can be caught, bred, or were distributed as an event Pokémon to Generation VI games. In addition, Mr. Rime can have the blue pentagon, due to Mime Jr. being able to have it.
The black clover (also known as the Alola symbol) is an origin mark that Pokémon obtained in the Nintendo 3DS Generation VII games have. Pokémon that were hatched, caught, or received as a gift in Pokémon Sun, Moon, Ultra Sun, or Ultra Moon have the black clover.
801 of the first 807 Pokémon can have the black clover, as only that many Pokémon can be caught, bred, or have been distributed as event Pokémon to Generation VII games. Unown, Deoxys, Keldeo, Genesect, Diancie, and Volcanion cannot have the black clover. In addition, Mr. Rime can have the black clover, due to Mime Jr. being able to have it.
Game Boy Icon
The Game Boy icon is an origin mark that Pokémon transferred from the Generation I and II Virtual Console games to Pokémon Bank via Poké Transporter have.
Only the first 251 Pokémon, as well as the 18 evolutions of these Pokémon introduced in later generations (that do not exclusively evolve from regional forms), can have the Game Boy origin mark.
The GO icon is an origin mark that Pokémon transferred from Pokémon GO have (whether transferred via GO Park or GO Transporter). While it is in the programming of the Nintendo 3DS Generation VII games, it was not used until Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!. It is a stylized G.
All Pokémon that can be obtained in Pokémon GO (except for Spinda), as well as their cross-generational evolutions, can have the GO origin mark.
Note: I only included marks present in SM/USUM, because that's the tag.
The other marks have no use except for a fun way to categorize Pokemon.
Markings have no explicit effect or purpose except what the player may invent for them.
In many online communities, players conventionally use them to mark which of a Pokémon's IVs are the maximum of 31; typically, the markings represent a maximum IV in HP, Attack, Defense, Special Attack, Special Defense, and Speed, in that order. Pink markings are often used to indicate IVs of 0.