From the official release announcement:
"Express your style and personality in League of Legends with chroma packs that reimagine original color schemes, allowing you to make your favorite champions and skins your own. Where skins offer alternate fantasies from a champion’s base thematic, chroma packs serve up new ways to personalize a specific champion or skin.
Designed with clarity in mind, each chroma pack is built around a themed palette of complementary colors and includes three chromas that modify either a champion’s base or one of their skins. As new optional cosmetic items that don’t impact balance or affect your ability to play the game, each of these initial packs will be available for 590 RP.
You can only unlock chroma packs for champions and skins you own. Head to the bundles tab of the store to unlock the chroma pack that suits you. Once you’ve picked up a chroma pack or two, your chromas will appear during champion select under the skins tab linked to the base champion or skin (at launch, chroma packs will not be available in Team Builder).
Change it up with these first run chroma packs:
Champion base and skin chroma packs
Lucian Prime base chroma pack
Garen Noble base chroma pack
Blitzcrank Steel base chroma pack
Fizz Scorch base chroma pack
Dragonfist Lee Sin skin chroma pack
Pool Party Leona Dawn skin chroma pack
Nemesis Jax Sand skin chroma pack
As a new product, we want to continue to improve chroma packs over time. We’re excited for players to get into game with them, and to hear even more feedback from the community. Still have questions? Click here to visit our Chroma Packs FAQ and we’ll see you on the battlefield!"
Click the links below to jump to previews for each chroma pack: