To think about prepositions, you start with their physical meanings: "The cat sits ON the table" says exactly where the cat is. "The cat is somewhere ABOUT the table" says the cat is not far from the table. Suppose in your project you study the dietary habits of fruit flies in the jungles of Brazil. Your project is on the dietary habits of fruit flies in the jungles of Brazil. Your project is about fruit flies. Your project is about insects. Your project is about flies. Your project is about Brazil. "About" is much more flexible. It is never a mistake to exchange them, but "on" works better with precision and "about" works better with approximation.

‘On’ and ‘about’ are similar but with ‘project’ I’d prefer ‘about’ or even other words, because projects are more open-ended. They might be ok if the nature of the project has already been described. On the other hand, My paper is on global warming. My paper is about global warming. are both natural and good. The choice between the two would be determined by whether the meaning is clear in context. ‘On’ can be followed by many different words. ‘About’ will alert you that a topic is coming.

'About' is the most grammatically correct word to choose. The word 'on' is another way to say the same thing that you will hear in spoken everyday American English. In written American English, you will see 'about.'