So color changes post reaction are usually ph induced; what is happening here is a change in oxidation states, which in turn changes valence electron configurations; which changes the ways photons interact with the molecules at a quantum level; this is called a chromatic shift.
it also may be do in part to being isolate converted material; isolate doesnt have the natural “antioxidants” that conventional distillates do; even high purity conventionally extracted distillates have trace impurities; without having “sacrificial oxidants” within the material; theres nothing to oxidize but cannabinoids; hence the rapid and consistent discoloration.
what i would do is; work on your neutralization; approach this stoichiometrically; also the addition of a small amount of conventional material will greatly reduce the rapid oxidation and will make the color more “natural”