ASSERTION: In a glass medium red light travels faster than blue light.
REASON: Red light has a wavelength larger than blue.

We know that $v=f\lambda$

Light's wavelength precisely correlates with its speed.
We are aware that the visible light spectrum has the following wavelengths, 

 violet < indigo < blue < green < yellow < orange < red.
Thus, it is clear that the wavelength of red light is far longer than that of blue light.
Thus, we might conclude that the justification is accurate.
Now, take into account that the speed of light in air (blue or red) is $v_a=c$
Let's think about the speed of light in glass (blue or red)

$V_g=\frac{c}{n_g}$=constant that is independent of light.

Therefore, we can conclude that both red and blue light move through glass at the same pace.
Consequently, we may state that this claim is false.