The correct answer is option 1: Both statements are individually true and statement II is the correct explanation of statement I.

Statement I states that the planet Neptune appears blue in color, which is true. If we observe images of Neptune captured by telescopes, it is evident that the planet has a distinct blue hue.

Statement II suggests that the presence of methane gas in Neptune`s atmosphere is responsible for its color, which is also true. Methane gas absorbs red light and reflects blue light, so when sunlight passes through Neptune`s methane-rich atmosphere, it scatters the blue light, giving the planet its blue appearance.

Option 2 is incorrect because statement II is indeed the correct explanation for statement I. Option 3 is also incorrect because statement I is true. Finally, option 4 is incorrect because statement I is true, as affirmed by images of Neptune, while statement II is also true, as methane`s role in coloring Neptune has been scientifically established.