As jonny says, this is UV light exposure (with possible acid etching from acid rain).
Jura is very dense as far as limestone goes, it's almost a marble and is often referred to as Jura Marble.
Are there any spare tiles left from this batch with banding? If there are then I'd suggested grinding and re honing the surface to see how it responds. I can't see you getting any joy with chemicals to be honest.
This looks likes a grind and finish job to me.
Take it up with the supplier of the stone also.
EDIT - Just noticed Jonny has already suggested this - I'd only read his first response.
what do you think of fact that the edges are lighter than middle of stone ?
it should the other way round .
do you think the unexposed edges in middle could still be damp.
i cant think of any other possibility.
the only other time i have seen this was on the jura job i mentioned i did 18 months ago.
i had a very serious problem with jura grey polished sweating under floor covering which builde put down. it got zebra stripes all over it and could not get off. marble shine ground and reploished whole ground floor to cure that problem.
but on the landings and stair cases which i did not do because i did not want to supply because of potential problems in this original post, some areas were covered and some not for many months.
when the final clean was made and all covers taken off the areas of stone up to say 6 inches off the skitings were lighter than the area that had benn covered and was still that way 18 months later.this is the opposite of what you would expect .
can you shed any lihght on this?