John Marshall (Option 1) was a British archaeologist, but he is more well-known for his work in the 20th century, particularly his role in the excavation of the ancient Indus Valley Civilization sites.

Alexander Greenlaw (Option 2) and J.F. Fleet (Option 3) were not prominently associated with the discovery of Vijayanagara ruins.

Colin Mackenzie (Option 4) was a British army officer and surveyor who documented and collected extensive historical and archaeological information about South India, including the Vijayanagara ruins, in the late 18th and early 19th centuries. However, the primary exploration and discovery of Vijayanagara ruins dates back to earlier periods.

The discovery of Vijayanagara ruins can be attributed to various early European travelers and adventurers, but it wasn't brought to light by any of the individuals mentioned in the options.

Therefore, the option [4] is correct.