The manufactures usually buy their plastics unpigmented and add color masterbatch to obtain the color required.
These can alter the properties of the plastic, https://en.wikipedia.org/wiki/Masterbatch White masterbatch contains titanium dioxide which is known to catalyze the UV degradation of plastics, which is why the Raptors turn yellow. Black masterbatch contains carbon black which inhibits UV degradation.
Many of the brands past and present didn’t / don’t make their own ski boots, there has always been a massive amount of sub-contracting. Atomic / Salomon have all their boots manufactured by a sub-contractor in Romania https://www.plastor.ro/en/products-and-technology/finished-goods-subcontracting/
That's really interesting, is that the case with all of the boots. As with skis it's always been the case that you'd see brand factory X making for brand y... I know Roxa do quite a lot, and someone recently told me who makes Fischer boots [and I am stuffed if i can recall] but...
Do the Romanian guys make all, or pretty much all of the Salomons and Atomics - it's usually been the case that the mfgrs try to keep the top/innovative stuff in house? Not doubting your information - if they make the lot as opposed to just [say] the bottom and middle models it's a really interesting story.
On the colours - bear in mind my Lange meeting was a number of years ago. At that point they had 'bought in' coloured pellets - I saw drums of blue ones and dipped my hands in 'em [and they came up with the 'blue is stiffer' line]. However things have probably moved on since them.