In the comics, blue kryptonite strengthens Clark's powers (and weakens Bizarro's.)
At the beginning of the episode Kara has just returned from a trip to Coast City with Jimmy Olsen. Coast City is the traditional home of future Green Lantern, Hal Jordan.
In the comics, blue kryptonite simply negated the effects of green kryptonite it didn't have any adverse affect on Superman.
Clark bears a striking resemblance to his biological father, as seen when Lara initially mistakes Clark/Kal-El for Jor-El.