The most appropriate statement about Gandhara art is that its theme is Indian, while its style is Greek. This means that the subject matter and content of the art are predominantly Indian in nature, but the artistic techniques and aesthetic elements used in creating the art are inspired by Greek artistic traditions.

Option 1 correctly identifies this relationship between the theme and style of Gandhara art. It highlights that the art explores Indian themes, such as Buddhist and Hindu religious figures and narratives, but incorporates the stylistic elements and influences from Greek art, which was introduced to the region through the conquests of Alexander the Great.

Option 2, which suggests the theme is Greek and the style is Indian, is incorrect. While Greek influences are present in Gandhara art, the primary themes and subject matter are rooted in Indian culture, not Greek.

Option 3, which claims that the theme and style are both Greek, is also incorrect. While Greek influence is evident in the style, the themes depicted in Gandhara art are distinctly Indian.

Option 4, which suggests that the theme and style are both Indian, is not accurate considering the Greek influence on the style.

Therefore, the correct answer is option 1.