Pokémon Adventures: Gold, Silver & Crystal

This chapter features the journeys of Yellow through Kanto trying to find Red after a beaten-up Pikachu (Red's) ends up at the doorstep at Oak's Lab. In the meantime of finding Red, Yellow gets attacked by the members of the Elite Four and their quest to make an all-Pokémon world.

(Source: Bulbapedia)

This chapter features the journeys of Ruby and Sapphire who are trying to conquer all the Pokémon Contests and Gyms in Hoenn respectively within the span of 80 days. However, this gets interrupted by two new evil organizations, the land-loving Team Magma and the sea-loving Team Aqua. Sapphire and Ruby have to worry about something else, too: their feelings for each other.

(Source: Bulbapedia)

It’s special round of the “Pokémon Adventures” manga taking place during Red and Gold's training on Mt. Silver.

When Professor Elm asked Gold to choose between three newly discovered Pokémon, never would he have expected to be chosen by a Pokémon instead! In order to become the Pokémon Champion, he has to challenge the Gym Leaders for the ownership of their badges. Meanwhile, Team Rocket emerges, returning to what they know best...plotting evil plans! To add to it all, a mysterious person in black thickens the plot...
(Source: Chuang-Yi).

Pokémon 4Koma: Gold and Silver is a one-volume Pokémon manga by Takahiro Yamashita. It is based on Pokémon Gold and Silver.

Red is just a normal kid living in the rural Pallet Town, when he decides to go out on his own adventure, along with his rival since childhood, Green. In this world of Pokemon, he makes many friends, humans and Pokemon alike. However, all is not well. Team Rocket is trying to capture Mew, a very rare Pokemon, and is performing experiments on other Pokemon, trying to increase their power. Red and his friends must battle against Team Rocket to stop their cruel experiments and unlock the secrets of Pokemon.