According to the
Mayo Clinic, colchicine can make a low platelet count (thrombocytopenia) worse, and it's also an issue for anyone with a low white blood cell count (neutropenia). They don't say whether the effect is long-lasting or it goes away once you stop taking colchicine, but your father's doctor may be able to tell you more about it.
Since your father's counts are still low, your biggest question may now be what they should do next for your father, whether or not colchicine contributed to the problem.
Are you able to talk to the doctor with your father or on behalf of your father? Since you obviously want to learn more about how to help him, I hope you can talk to the doctor directly and get your questions answered.