In the rectangular coordinate plane below, a red square with one side on the $y$-axis and a blue square with one side on the $x$-axis share a common vertex.
One vertex of each of the red and blue squares lies on the line $\dfrac{x}{2} + \dfrac{y}{3} = 1$.
According to this, what is the side length of the red square in units?
A) $\dfrac{14}{15}$
B) $\dfrac{15}{16}$
C) $\dfrac{16}{17}$
D) $\dfrac{17}{18}$
E) $\dfrac{18}{19}$