Can I play Blue's Tactics if I have more than 8 cards in my hand?
Yes, because you could still have less than 8 cards in your hand by the end of your turn.
Source: Unified Minds FAQ (2019-07-19), TPCi Rules Team (2019-08-01)

Relevant cards

Note: All applicable cards may not be listed below.
SM11_188
SM11_188
SM11_231
SM11_231