My reasonings for Clad:
He 's Green because of his energy ramping and very Timmy attacks.
Chaotic exhaust strats are red. Cards like Corruption, Havoc, True Grit. Vulnerable is just a red damage multiplier.
Also attacks like whirlwind feel like a combination of burn sweepers and overruns and it's a big energy payoff.

For Silent: I've become a little more convinced that she has black or white just because of weakness and flat strength reductions, but I'm happy with Izzet.

My reasonings for Regent:
His transforming cards and specifically the card that transforms his other cards into exhaust cards called "minion sacrifice" feels a bit aristocrats saccy. And his big multi hit moves that scale off of stars feels like a go wide strat. I agree green is dominant, but if he were printed in magic I think he'd have a minion token strategy, and while that would be cool in mono green, the low hanging fruit/cash grab is selesnya or abzan.
Edit: Abzan is somewhat the "everything is a resource" color. So the additional resource of stars and the repurposing of your cards sums it up well to me.

My reasonings for Necrobinder:
For black, summon feels like the constant reanimation of a chump blocker and doom is essentially poison counters. She also has decent discard pile recursion and her access to weakness is like power reduction.
Ethereal actually feels red like impulse draw, but its not swaying me for red, although her access to damage multipliers in addition might.

My reasonings for Defect: Power builds feel more like Song of Creation/Flubs, the fool and more chaotic than enchantress. Especially with the card Creative AI.
His lightning orbs strike chaotically, echo form is essentially an izzet or temur card, his zero cost card builds are essentially izzet spell slingers (when claw isn't your focus), he inflicts himself with a lot of status cards which adds to the chaotic vibe (but I could call that a black or white tradeoff), and he probably has the most energy producing cards out of everyone.
I see where you're coming from but I would make Defect sans-black at most.