Think of marching band members walking at different speeds through mud: those taking longer strides (like long-wavelength red light) face less resistance and steer less off course compared to short-striding members.

Remember 'VIBGYOR' from bottom to top on the screen: Violet is at the bottom (most deviated), Red is at the top (least deviated).

According to Cauchy's dispersion formula, the refractive index ($\mu$) of a medium decreases with an increase in wavelength ($\lambda$). Since red light has the maximum wavelength in the visible spectrum ($\lambda_{\text{red}} \approx 700\text{ nm}$), its refractive index in glass is the lowest. By Snell's Law, deviation ($\delta = i - r$) is directly related to refractive index; hence, minimum refractive index results in minimum deviation for red light.

Remember that deviation ($\delta$) is inversely proportional to wavelength ($\lambda$). Whenever an exam asks about least deviation, always pick the colour with the longest wavelength available in the options (Red > Yellow > Green > Blue > Violet).