The main ability of these cards is 'Teamwork', meaning that their attack and defence are increased when more of them are on the field, as a limter, I've specified that each monster must be different, and they don't receive the bonus from themselves. It's about 200 per monster, for a maximum of 800 extra attack and defence.
Each card is listed with their effect stated below the image just in case you can't read the effect text in the image itself.
ShinkenRed
Spoiler
Effect:
This monster's ATK and DEF increase by 200 for each different 'Sentai' Monster currently on this card's controller's side of the field, other than this card. When this card is summoned, place 1 'Sentai Counter' on this card (Max. 3). Remove 1 'Sentai Counter' on this card to add an equip spell with 'Shinkenger' in it's name from your deck to your hand.This effect can only be used once per turn.
ShinkenBlue
Spoiler
Effect:
This monster's ATK and DEF increase by 200 for each different 'Sentai' Monster currently on this card's controller's side of the field other than this card. When this card is summoned, place 1 'Sentai Counter' on this card (Max. 3). Remove 1 'Sentai Counter' on this card to to special summon a Machine type monster with 'Shinkenger' in its name. That monster cannot attack this turn. This effect can only be used once per turn.
ShinkenPink
Spoiler
Effect:
This monster's ATK and DEF increase by 200 for each different 'Sentai' Monster currently on this card's controller's side of the field other than this card. When this card is summoned, place 1 'Sentai Counter' on this card (Max. 3). Remove 1 'Sentai Counter' on this card to return one monster on the opponent's field to its owner's hand. This effect can only be used once per turn.
ShinkenGreen
Spoiler
Effect:
This monster's ATK and DEF increase by 200 for each different 'Sentai' Monster currently on this card's controller's side of the field other than this card. When this card is summoned, place 1 'Sentai Counter' on this card (Max. 3). Remove 1 'Sentai Counter' on this card to remove from play 1 spell or trap card on the opponent's side of the field until the end of their next turn. This effect can only be used once per turn.
ShinkenYellow
Spoiler
Effect:
This monster's ATK and DEF increase by 200 for each different 'Sentai' Monster currently on this card's controller's side of the field other than this card. When this card is summoned, place 1 'Sentai Counter' on this card (Max. 3). Remove 1 'Sentai Counter' on this card to send 1 spell or trap card on the opponent's side of the field to the graveyard. This effect can only be used once per turn.
So, what do you think, be sure to let me know because Gold and some support cards are on the way.
EDIT: Yellow is now working.