Hi
My jpw is showing some yellowing of the needles. It has already casted all the old needles but the new needles show a yellowish tint. The overall state of the tree is healthy. It has produce many new buds and back buds. The soil mixture is made up of 50/50 akadama and kiryu. The tree is planted in a colander so I doubt the problem could be with lack of air in the roots. I have been fertilizing quite heavily. I wander if this could the reason… always used organic slow release. Here is a pic
I have a young JWP that is showing the same thing. I planted the tree in my garden a few weeks ago to endure the winter. It was looking yellowish at the time, but the needles were very solid on the branches. They wouldn’t pull off. I checked it yesterday and it’s still the same. I think it may just be a characteristic of the variety of JWP.
Could be seasonal?
I keep mine on the dryer side in the cold.
Possibly but it looked a bit pale also during growing season…
I always think of reducing watering when this happens (pines related)
It it doesn’t stop and you think it keeps yellowing then do some further checks in the soil. If needles are yellowing evenly and not drying/falling there is something going on in the underground (judging acc the picture and your mentioning of needles not falling off only tho!) do some research on diseases if it gets worse.
Hope this bit helps 
Maybe the tree was made from seed/cutting?
Those are often more on the yellowish side!
Best regards from Austria
