What are the official rules for modified champion deck format - specifically, are you locked to your champion deck's colors, or can you use cards from additional colors opened in booster packs?

Ruling: The deck must be a comp-legal deck, and you can use the additional packs to help make your 40-card deck.

Nuances:

• These rules are not in any official document from Riot
• Event organizers may explain specific rules at their events, and implementation might differ between stores
• Riot has not provided a precise official explanation of how the format is intended to work