I personally see it this way -

Black as a color features necromantic power and decay. We see faster ways from the graveyard to the battlefield, but it's either at a cost or it's just a corpse. When we look at cards like Animate Dead, you have an enchantment literally animating the body, but if you nullify the magic moving it around, it goes back into the graveyard. A spell like Reanimate you exchange life force to put them back into play. You have Victimize where a profane ritual is being conducted and you must sacrifice a creature of yours to bring others back and they come back tapped like they're slowly getting back up.

White as a color features holy light and actual restorative power. White doesn't just bring back creatures, but also enchantments and artifacts. Brilliant Restoration returns all artifacts and enchantments from your graveyard to the battlefield and we get flavor text describing healing the land. Your mechanical battlefield where magic and structures have been destroyed is now seeing all of that returned showing card art of a divine spirit dragon. You also see cards with this "rescue" theme like the creatures were on death's door, but someone intervened either delivering first aid or some quick healing spell. Moorland Rescuer dies and then you get back creatures with less power than it like it was saving weaker beings heroically in battle. Finally we see the spirit outlive the body with white

Green as a color is more true to the cycle of life. The easiest card type to recur in green is land. Crucible Of Worlds, Conduit Of Worlds, Ramunap Excavator we're playing lands straight from the graveyard into play. Basically any other card type we can get, but they go back to hand instead of onto the battlefield. You need to go through the process of casting these cards again like you need to cultivate them from the beginning again. Recollect is an example of this with a simple return target card from your graveyard to hand. The flavor text talks about bones of the past telling their tales like their knowledge can be used again.