Taxing effects can be usually seen in white color, but here it is in blue. Probably Wizards of the Coast decided to diversify a bit, which is a welcome move, when it comes to such valuable planeswalkers like Kasmina.
Her minus ability can make two or more tokens, if you run proliferate cards in your deck. At the same time she is protected by her passive ability, which also includes your creatures.
Overall, a great addition to your blue deck.