A small New York City cafe is taking on coffee giant Starbucks in a legal war of the unicorns. The End Brooklyn in a new lawsuit accuses Starbucks of trademark infringement, arguing that the color-changing “Unicorn Frappuccino” recently introduced by the Seattle chain overshadows the smaller company’s health-conscious “Unicorn Latte.” The End started selling the Unicorn Latte in December, and has had a trademark application for the drink name pending since January, the company said in a Brooklyn federal court complaint filed Wednesday. Starbucks launched the Unicorn Frappuccino in April as a limited-run item. The sweet offering quickly …