Question

I prefer blue jeans than black one

Answer 1

Blue jeans rather than black ones were being preferred by me.

Answer 2

I prefer blue jeans than black one. It can alternatively be said that I prefer blue jeans over the black one.

In the both ways, these two sentences will make the same sense.

Where there are two options to choose from, we can use either ‘over’ or ‘than’ to hint at the difference. Both the sentences are correct and can be very well used.