I like the concept but each of the colours already has far more efficient and less conditional ways of getting the above effects.
Taking the White one as an example, I can pay 4 mana and do 3 damage to attacking creatures (Hail of arrows). I don't need any creatures. Or cast Wing Shards. I accept that you have added the ability to use it when attacking, although you need a creature or two to stay at home meaning this is very conditional.
I think these can be safely powered up a little, I suggest taking out the conditions
Strike of Flowing Water


{U}
Sorcery
As an additional cost to cast Strike of Flowing Water, tap an untapped creature you control.
Tap any number of target creatures. Creatures don't untap during target players next untap step.
Revanche Technique

{W}{W}
Instant
As an additional cost to cast Revanche Technique, tap any number of untapped creatures you control.
Deal damage equal to the total power of the tapped creatures divided as you choose among any number of target attacking or blocking creatures.
Bite of the Recluse


{B}
Sorcery
As an additional cost to cast Bite of the Recluse, tap an untapped creature you control.
Destroy any number of target creatures that were dealt damage this turn.
Lightning Technique


{R}
Sorcery
As an additional cost to cast Lightning Technique, tap any number of untapped creatures you control.
Deal damage equal to the total power of the tapped creatures to target creature or player.
Willow Strike

{G}{G}
Sorcery
As an additional cost to play Willow Strike, tap an untapped creature you control.
Destroy any number of target artifact creatures.
Taking the Red one as an example. If I have 5 power of creatures, I'll damn well attack with them. If I want a Lava Axe I'll cast one. Even without the Haste restriction, I think this is pretty weak. With it, it is terrible.
Of course it is fine to make weak cards for flavour reasons......