Answer
Yellow light.
Work Step by Step
The fringes will be spaced farther apart when the longer-wavelength yellow light is used.
The equation at the bottom of page 550 explains this.
$$\lambda = d sin \theta$$
Suppose we use a longer wavelength, $\lambda$. The left-hand side of the equation is larger, so the right-hand side must be larger too.
The distance between the slits, d, is fixed. The longer wavelength gives a more spread-out pattern, i.e., $\theta$ increases, because sin $\theta$ increases.