Bulbapedia has an extensive article on it, but it boils down to, in Generation III and on, there is no difference in stats between normal Pokemon and shiny ones.
Generation II (Gold, Silver, and Crystal) is the exception because shininess is determined based on the stats of the Pokemon. Namely:
If a Pokémon's Speed, Defense, and Special IVs are 10, and its Attack IV is 2, 3, 6, 7, 10, 11, 14 or 15, it will be Shiny
But, from Generation III and onward, it is determined based on a secret ID and a trainer ID, so it has nothing at all to do with the stats and will be just like every other Pokemon.
Something fun to note is that if the Male/Female ratio is 7:1, in Generation II, you cannot have a female shiny Pokemon because of the way it is calculated.
Each unique Pokémon sprite has exactly one normal palette and one shiny palette. However, some Pokémon have more than one possible sprite, due to gender, variants, or alternate formes. Each of those can have a different shiny palette.
For example:
- Frillish♂ is blue, but Frillish♀ is pink. Shiny Frillish♂ is teal, while shiny Frillish♀ is salmon pink.
- Basculin can appear as red-striped or blue-striped. Shiny red-striped Basculin has an orange stripe, while shiny blue-striped Basculin has a light blue stripe.
- Shellos found in west Sinnoh are pink, but Shellos found in east Sinnoh are blue. Shiny Shellos are salmon pink in west Sinnoh, and cyan in east Sinnoh.
Generally speaking, if a Pokémon can be found in multiple different colours, its shinies will have different colours from each other.
Further, some shiny Pokémon's evolved forms have very different colour schemes, even if the original Pokémon all had the same colour.
- Shiny Charmander and Charmeleon are yellow, but shiny Charizard is black. (A shiny Charmander will always hatch yellow, and when it evolves to Charizard will always turn black.)
- Shiny Magikarp is gold, but shiny Gyarados is red.
Best Answer
Shiny Pokémon can be encountered in any core-series game from Gold and Silver onward. "Shinies" are Pokémon that have an alternate coloration from others in its species.
What is a Shiny
Whenever a Pokémon is generated by the game, there is a slight, fixed random chance that it will be shiny. This chance can be raised in certain circumstances; see the remaining sections.
"Generated" means:
Pokémon retain their shiny status through evolution and form changes. However, the exact coloration may be different (e.g., Shiny Charmander is yellow, Shiny Charizard is black).
Shiny Pokémon are indicated by a sparkling animation when they appear in battle, and a star or sparkle symbol on their status screen.
Each Pokémon form has precisely one alternate shiny coloration, and they differ only by color.
Charizard, Shiny Charizard
What is Not a Shiny
Shiny Pokémon are not to be confused with form differences or gender differences, which a handful of species have, and sometimes look very similar to shinies. Each form will have its own shiny variation, as well. For instance, Shellos has two forms, which differ both in color and head design.
West Shellos, Shiny West Shellos
East Shellos, Shiny East Shellos
Additionally, the N64 Stadium games will give slight alternate coloration to Pokémon with certain nicknames. These are not shinies, and in fact, Stadium 2 features both shinies (called "Color Pokémon") and these nickname-variations concurrently.
Finally, though all games have programming for shiny versions of all Pokémon, there are a few instances where a Pokémon will never be shiny, which are noted below.
Generation I - Red, Green, Blue, Yellow (Game Boy)
There is no direct support for shiny Pokémon in these games.
However, for compatibility reasons, the data that Generation II uses to determine shininess is also available in Generation I. Therefore, it could be said that Generation I does have Shinies, they just don't appear as such until they are traded forward. See the next section for why this is.
Generation II - Gold, Silver, Crystal (Game Boy Color)
The chance for wild encounters and NPC gifts being shiny is
0.012%.To preserve backward compatibility with Generation I, this information is encoded in part of the Pokémon's hidden statistical information, called Individual Values (IVs). This means that Generation I Pokémon, when traded to Generation II, also have a
0.012%chance of being shiny, and shiny Pokémon remain shiny across trades, even to Generation I.Increased Rates
Pokémon hatched from eggs inherit IVs from their parents, meaning the chances can be skewed as high as
1.56%in certain circumstances.The Crystal-exclusive Odd Egg has an increased chance of producing a shiny:
14%internationally,50%in the Japanese version.Guaranteed Encounters
Each game has a single Pokémon that is always shiny: a Gyarados in the middle of the Lake of Rage, encountered as part of the story.
Excluded Pokémon
Due to the way IVs are used for multiple things in these games, a few shinies are impossible:
Generation III - Ruby, Sapphire, Emerald, FireRed, LeafGreen (Game Boy Advance)
The chance for wild encounters, NPC gifts, and hatched eggs being shiny is
0.012%.The data structure was overhauled in Ruby and Sapphire, separating battle statistics from shininess. The shiny calculation has thus been revamped, producing the same probability without being tied to gameplay-altering statistics.
Generation IV - Diamond, Pearl, Platinum, HeartGold, SoulSilver (DS)
The chance for wild encounters, NPC gifts, and hatched eggs being shiny is still
0.012%.Increased Rates
New is the so-called "Masuda method" (named after the developer who hinted at it to players): if two Pokémon are originally from two different real-world countries and can breed, the probability of their eggs producing shiny Pokémon is raised to
0.061%.The post-game of Diamond, Pearl, and Platinum gives the player the Poké Radar item, which is used to create special shaking-grass encounters. Chaining these encounters together increases the probability that one of those grass patches will sparkle, guaranteeing a shiny encounter there. The probability rises as high as
0.5%, after a 40-length chain. Unfortunately, this item isn't available in HeartGold and SoulSilver.Guaranteed Encounters
As HeartGold and SoulSilver are remakes of Gold, Silver, and Crystal, they also have a fixed encounter with a shiny Gyarados. Unlike the original version, though, if you defeat it, it will reappear after you beat Lance.
Generation V - Black, White, Black 2, White 2 (DSi)
The chance for wild encounters, NPC gifts, and hatched eggs being shiny is once again
0.012%.Increased Rates
The Masuda method probability has risen to
0.073%.In Black 2 and White 2 only, if you manage to catch all non-event Pokémon in the National Pokédex, you will receive the Shiny Charm, which automatically raises all shiny probabilities by
0.024%.Guaranteed Encounters
Black 2 and White 2 have two guaranteed shinies:
Excluded Pokémon
Three Pokémon are unable to be shiny:
Generation VI - X and Y (3DS)
The chance for wild encounters, NPC gifts, and hatched eggs being shiny has risen to
0.024%.Increased Rates
If you stand in the same spot and continually use a fishing rod, and get a hit every time, the rate apparently increases (the exact rate is not yet known).
The Friend Safari, a post-game venue, has a higher chance of shiny encounters (estimated to be
0.195%). However, it is not affected by the Shiny Charm (below).The following return from previous generations. Bulbapedia hypothesizes that the rates are simply double from their earlier rates, but this appears to not be 100% proven.
0.146%)0.073%)Excluded Pokémon
Summary
Gen. | Base | Masuda| Extra | % | % | Chances --------|-------|-------|------- I (GB) | N/A | N/A | II (GBC)| .012 | N/A | = 100%: Story Gyarados = 14%: Odd Egg (C) III(GBA)| .012 | N/A | IV (DS) | .012 | .061 | = up to 0.5%: Radar (D/P/P) = 100%: Story Gyarados (HG/SS) V (DSi) | .012 | .073 | = 100%: Prize Gible (B2) = 100%: Prize Dratini (W2) = 100%: Prize Haxorus (B2/W2) + 0.024%: Shiny Charm (B2/W2) VI (3DS)| .024 | .146* | = up to ??%: Fishing = 0.195%: Friend Safari + 0.073%: Shiny Charm (except for Friend Safari) * estimated* I'm unsure of the details on when Roaming Pokémon are generated. If anyone has additional information, please comment!