A bag contains blue, green, and yellow balls totaling 10 balls. Two balls are randomly drawn from the bag (each ball has an equal probability of being drawn). The probability that both balls drawn are blue is $\frac{1}{15}$, and the probability that both are green is $\frac{2}{9}$. The probability that two randomly drawn balls are of different colors is $\frac{\text{(16--1)}}{\text{(16--3)}}$. (Express as a fraction in lowest terms)