I described it as looking into the sun then looking away, you see colours, they aren't directly blocking your vision they are sort of around your vision. Words blur randomly and while there are times of the day where it can be pretty bad sometimes it seems to go away completley and my vision is crystal clear.
I had optic neuritis last year with my initial relapse (many other symptoms too). it lasted for several weeks while they did tests to confirm it was ms and then I took 5 days of methylprednisolone 500mg a day (strong enough to make a horse happy). within a few days of being on those tablets my optic neuritis cleared up completely.
My vision isn't perfect but I don't have any problems focusing anymore and don't see colours now. I don't know if it ever becomes permanent but thankfully mine was not that time. Best mention it to your doctor or ms nurse and see if they can help you sort it out.