While Devotion has replaced Chroma for the forseeable future, Chroma, as an ability word, has the vital option of versatility in how it's applied. While Springjack Shepherd could just as easily have been Devotion,
Light from Within exemplifies where the ability word has an advantage, as it has a per-target effect based on that particular target's variable.
Phosphorescent Feast has you reveal cards and checks among those, which can be non-permanents. For an example of an extreme:
Deatheater Cinder 1bb
Creature - Elemental
Flash, Wither
Chroma - When Deatheater Cinder enters the battlefield, put a +1/+1 counter on it for each Black mana symbol on Sorceries and Instants you control.
1/3
If I understand the stack properly (basically, if the Chroma effect is added to the stack immediately after this spell resolves, before anything else does, and the mana costs are preserved on the stack), this particular example fetches you value off a stack of Instants and Sorceries
regardless of if they resolve or not, as the effect will resolve before they actually leave the stack. So you could play this after a counter war in Blue/Black control to salvage your removal and discard mana.
Meanwhile, in some specific Red/Black setups, one could clone high-cost reanimation or removal to give this a very large bonus, as the copied Instants and Sorceries would keep their Black mana symbols. But as this requires the stack, you need to invest a large amount of mana into Black mana symbols
before you cast this, making it useful only following other spells, and thus
nearly worthless as a three-drop on its own. Especially since it's Toughness biased
and understatted.
This is something that Devotion
cannot do, as Devotion is fixed in what it counts from.
However, as Devotion is a player quality, it can then be manipulated by other card effects. For example:
Raidpyre Soothsayer 2(b/r)
Creature - Minotaur Shaman
Mana costs of creatures in your graveyard count for your Devotion to Red and to Black.
1/1
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This card is enormously overcosted on its own, but radically accelerates the deck it goes in. While it's three mana for one devotion,
on its own, it trivially offers more devotion than its mana cost once the game gets going, allowing you to throw away creatures freely without worrying about losing Devotion. It expands applicability in ways that would be far more complicated and prone to errata confusion for Chroma, as ability words aren't mechanical objects.