As several others have pointed out, blue jean is a different colour in different leathers. I agree with hermesmonkey that BJ is lovey in clemence and togo. It is a deeper, richer shade than in epsom, where it is lighter, cooler and flatter.
In togo (which is where I have it), the deepness of the blue makes is suitable for winter wear. In fact, it actually makes me happy to pull it out when the world in drab and grey - the pop of colour against the greys and blacks I seem to live in for the whole winter season really is striking. It also looks great in the summer.
I disagree that ciel is a better neutral - too light and cool for the insipid colours of winter.
I love indigo also, an amazing neutral, but it might be too dark for what you are looking for.