I feel like most think Chromatic Dragons are evil because they worship Tiamat instead of Bahumat, Tiamat is a goddess of Chaos which most people generally associate with acts of evil but chaos generally isn't evil it just is. While Bahumat the metallic god of Order is generally seen as good there are times when too much Order is stifling
Well to start, if I were to write Tiamat or Bahamut for whatever reason, I'd wouldn't try to stray too far from their moralities. I mean it's right there in their titles: Tiamat, Queen of the Evil Dragons and Bahamut, King of the Good Dragons. It's practically written in their DNA and concept. So trying to portray Tiamat as some woobie or Bahamut as being secretly evil would defeat the entire purpose of the characters.
I wouldn't even say that Tiamat is a Goddess of Chaos in a traditional sense. Chaos usually means the potential for change and the hope for a better future. Tiamat on the other hand seems to lean more to the "evil" in "chaotic evil". As in she's fully willing to commit to atrocities in order to further her goals. And indulge in her own whims and impulses instead of tearing down an oppressive order. Hell, for a Goddess of Chaos, she keeps a tight leash on her servants and has very problems with dominating them when they get too uppity. Aren't the Blue Dragons (Lawful Evil) amongst her most dedicated followers?
As a whole, I don't think Tiamat represents Chaos as a force for change. But rather as a force for shortsighted impulses and domination. She's the one who would dominate and use her domination as an excuse to indulge in her vices. Think a dragon version of a Skeksis and you get the drill.
Conversely, Bahamut is a bit closer to the "good" in "lawful good". His sphere of influence centers around justice, doing good deeds, and promoting acts of charity. He's not even focused on establishing some kind of societal order or regime since he rarely gets involved with mortals on a societal level. Usually, Bahamut only acts to right some kind of wrong or bring justice (which tends to be against his sister and her followers). In that way, he's more of a knight-errant than a king.
If Tiamat represents domination and living out one's impulses for the self, Bahamut focuses on helping others and holding the self to a higher standard. In that regard, the "lawful" is less societal and more living to a code of honor or strong morality. And their relationship is less "chaos vs order" and more "depravity vs nobility".
So with all this in mind, how would I handle Chromatics as a whole if it's less a societal standard and more a moral standard? Well to start, I sincerely doubt the Chromatics have too much love for Tiamat. Again, she keeps a tight leash on them and expects things like accepting consorts from them or reaping whatever portion of their hoards they have collected. And I did read that some Chromatics will try to keep portions of their hoard secret to keep out of Tiamat's hands. From this, I believe that their devotion to Tiamat is less out of reverence and loyalty and more wanting to stay on her good side. Thus, the idea of leaving her has to be a thought a lot of the Chromatics have.
Thing is, Tiamat is freakishly powerful and I doubt she'd want any of her children to get any ideas of rebelling. Even if somehow a Chromatic could break away from Tiamat and survive, they were still raised with the toxic mindset that their "mother" instilled in them. So it would be a pretty painful changing process if all they know how to be are vicious monsters. Add to that how many mortals rightfully think Chromatics are violent monsters, and you have a stacked deck.
Again, I do believe it is possible. It just won't be easy. If I were to write this sort of story, I would possibly have a young Chromatic who strikes out on their own from their parents who instilled that toxic mindset. Old enough to be self-sufficient, but young enough to still be mentally vulnerable and a bit awkward in terms of actually being vile. Basically enough of a threat to gain adventurers' notice, but not enough of a threat to have a massive bounty on their heads. From then, you could either see them begin to question themselves on what they're doing wrong. Not sure how Bahamut might see such a dragon though. On the one hand, forgiveness and mercy are part of his sphere. On the other, I did read that he was also pretty merciless when it comes to Chromatics (I mean, he's been in conflict with Tiamat and her brood for so long that it's hard to blame him). So it could go either way.
That's how I'd write the dynamic between Tiamat and Bahamut along with the Chromatics. Let me know what you guys think or if I'm missing something.