Back 4 Blood Card System Guide: What You Need to Know

Blue Colour Cards Cross trainers +10% Stamina Rhythmic breathing +30% Stamina
-20% Slow Resistance Reload drills +10% Reload Speed Mag coupler +30% Reload Speed
Disables: Aim Down Sights Meth head +60% Melee Attack Speed
+60% Melee Stamina Efficiency
-30% Trauma Resistance Ridden slayer +10% Weakspot Damage Reckless strategy +20% Weakspot Damage
-5% Damage Resistance Shooting gloves +10% Weapon Swap Speed Smelling salts +25% Revive Speed Dash +5% Move Speed Superior cardio +15% Sprint Efficiency Breakout Automatically break out of a grab 1 time per level. Combat knife Turns your Bash into a Knife that counts as a melee weapon. Dance all day +10% Movement Speed
No Movement Penalty for strafe and backpedal.
Disables: Sprint Team stamina +10% Team Stamina
This card applies to you and your teammates. Uzi Grants you an Uzi starting weapon. Pep in your step Precision kills grant you 10% Movement Speed for 4 seconds. Utility scavenger You can sense nearby Utility Accessories.
More Utility Accessories spawn. Red Colour Cards Ammo pouch +10% Ammo Capacity Front sight focus +10% Accuracy Quick kill +30% Accuracy
Disables: Aim Down Sights Antibiotic ointment +15% Healing Efficiency EMT bag +30% Healing Efficiency
-10% Stamina Efficiency Blood donor When you or your teammate becomes incapacitated, all teammates heal for 45 health over 10 seconds.
This card applies to you and your teammates. Caretaker Healing a teammate also heals you for 100% of the amount healed. Hunker down While crouching, gain 20% Damage Resistance and 12.5% Accuracy. Martyr When you or your teammate becomes incapacitated, all teammates gain 100% Damage, 20% Reload Speed, and Unlimited Ammo for 10 seconds.
This card applies to you and your teammates. Team ammo +10% Team Ammo Capacity
This card applies to you and your teammates. AK47 Grants you an AK47 starting weapon. TAC14 Grants you a TAC14 starting weapon. Down in front! While crouching, gain 10% Damage Resistance and 100% Friendly Fire Resistance. M1A Grants you an M1A starting weapon. Ammo scavenger You can sense nearby Ammo.
More Ammo spawns Weapon scavenger You can sense nearby Weapons
More Weapons spawn. Support scavenger You can sense nearby Support Accessories
More Support Accessories spawn. Green Colour Cards Vitamins +10% Health Canned goods +30% Health
-10% Stamina Batter up +25% Melee Damage
+25% Melee Cleave Power Mean drunk +75% Melee Damage
+75% Melee Cleave Power
-50% Gun Accuracy Berserker Gain 10% Melee Damage, 10% Melee Speed, and 5% Movement Speed for each Melee kill in the last 4 seconds. Pyro +75% Fire Resistance
Kills with fire grant you 3 Temporary Health. Sapper +100% Explosive Damage
+50% Explosive Resistance Triumph Kills with a melee weapons heal 2 Health. Team health +10% Team Health
This card applies to you and your teammates. Heavy attack Charge: Hold LMB with melee weapons to burst forward.
Charge attacks deal 100% increased damage. Sunder Melee hits cause the target to take 20% increased damage 5 seconds. Arsenal You can equip a Primary weapon in your Secondary slot. Offensive scavenger You can sense nearby Offensive Accessories.
More Offensive Accessories spawn. Yellow Colour Cards Grenade pouch +1 Offensive Inventory Fanny pack +1 Support Inventory Finders keepers Pistol kills have a 2% chance to spawn ammo. Gunslinger When you stow your weapon, it reloads. Trophy Hunter When you kill a Mutation, gain 10 Copper (up to 300 per level).
This card applies to you and your teammates. Resourceful Your secondary weapons have unlimited ammo. Insurance policy +1 Extra Life
Lose 50 Copper at each Saferoom Living on a prayer Kills while at critical health recover 1 health. Lucky duck Whenever your team loots Copper, you have a 35% chance to find 35% additional Copper. Wake of death You can shoot while sprinting. Overheal Healing that exceeds your maximum Health will grant Temporary Health. Copper scavenger You can sense nearby Copper.
More Copper Piles spawn. Saferoom recovery Your team heals 5 Trauma Damage and refills 10% Ammo in each Saferoom.
This card applies to you and your teammates.

Source: https://www.talkesport.com/guides/back-4-blood-card-system-guide-all-you-need-to-know/