This is a paid game, people will complain about lives but it makes sense. – Color Code - Synesthesia Trainer Review

The lives make sense. If you want to learn as important a skill or ability as synesthesia, you are going to have to stagger your training and actually associate colors to letter/numbers. This isn't something you can cram. That's not how learning works. That is also not how the brain works. If you want to make pathways in the brain (which is what synesthesia is) you're going to have to put in the effort and stagger the training, which is why the lives make sense. The more you gain the skill, the less you will lose lives. It makes such perfect sense.
Review by Rjected on Color Code - Synesthesia Trainer.