From Bulbapedia, the community-driven Pokémon encyclopedia.
The Easy-to-Build Colorless Deck is a predominantly and type deck found in the Team Rocket Strategy Guide. The deck is considered easy-to-build as it contains few rare cards, with the aim that a player of any age or skill level could complete it.
This easy-to-build deck uses mostly Colorless Pokémon with some Fire Pokémon added in. After the first few turns, your opponent will think your deck isn't working very well. That's because you'll have several Colorless Pokémon in play, and most of your Energy will be Fire Energy. Your opponent will think you're having trouble drawing Fire Pokémon. That's okay. What your opponent doesn't know is that your deck is working just fine.
If your opponent is playing a Fighting or Lightning deck, be careful. Most of your Pokémon have a Weakness to one of those two types of Pokémon. Your Pokémon also have a resistance to Fighting or Psychic Pokémon. Make sure that you use that to your advantage. If your opponent is playing a Grass deck, some of his or her Pokémon will have a Weakness to Fire. Use Flareon and Charmander to take advantage of that Weakness.