I basically keep to the various themes, minus blues (who, it never made any sense to me would be desert-based). But for a long time now, I've associated chromatics in my setting world with the various "deadly sins." Now, of course, the world has its own cosmologies, pantheon (no Abrahamic religions), and such so the concept of "Seven Deadly Sins" as we understand them doesn't really exist.
Evil Dragons, themselves, are the corrupted, "diminished," versions of metallic dragons, who are themselves "lessened" from their roots as an original creation from the birth of the world/setting/creation as "the Great/Elder Wyrms." So they are all tainted with things like greed and pride and wrath...on a cataclysmic elemental level. Thankfully, over the eons, that power has dissipated greatly to a point where pitiful creatures, like mortal humans and dwarves can actually do them harm. But they re still formidable primordial (meaning "primal/original/uncontrollable", not primordial in the creature category sense) creatures.
So, while each type of chromatic dragon is possessed of a great collection of the worst ("evil") impulses of creation, each individual color is more attuned and exhibiting of a particular vice. All that in mind...
Reds: most obviously (and seems from this thread, universally accepted) are the most powerful and dangerous. The most unabashed in destruction and cruelty. They get two. Wrath (unsurprisingly) and Avarice (greed) are the guiding all-consuming themes of the Red dragons. Thankfully, in my world, there are only very few who have been known in the world...and so, it is assumed, only very few left, if any.
Blues: are generally considered the second most dangerous and powerful...Sleeker, faster, more intelligent and of course more aesthetically pleasing (according to them) than reds, blues are maniacal schemers everseeking to increase their power, the wealth of their horde, and impressiveness of their territory. That others (especially other dragons!) consider blues SECOND in the hierarchy of dragonkind drives blues mad, as their own superiority is indisputable to their eyes. Pride is the overriding vice of a blue, followed closely by vanity (which is not, technically, one of the Seven Sins). They prefer the mountaintops (while those great lummoxes, the reds, tunnel beneath the ground and inhabit volcanoes where no one will see their glory, fools enough to entomb their draconic greatness.). Especially along coastlines and/or near large lakes. Somewhere that they can easily take to the air and revel in the great storms that often accompany their arrival and are to be found frequently lingering in their territories.
Greens: everyone's favorite manipulative mindf**kers (thank you original Dragonlance) are the lords of the deep forests, holding court over their dominated, charmed, and just plain manipulated thralls. They are the dragons most closely tied to Sloth. Why exert the effort when you can just enthrall others to do it for you? Lie (and lay!) in comfort among the green growing things, the eternal trees and ferns that just ever so slowly creep, continuing unabated without really having to DO anything. Just soak up the sun. Loll from one side to the other, to warm your scales in the sun as it crosses the sky. Let your slaves bring you riches, defend your lands, bring your food/victims to play with and expand your yoke. Why should anything so grand and wondrous as a Green Dragon deign to lift a claw to deal with the less-than-specks that now infest the world. Clearly, every other species are THERE to be controlled and make draconic life easier. As noted, enchantments are the green's bread and butter. I add mental/telepathic powers, hypnotic gaze, and the like. Greens, essentially, /are/ sloth. They will probably be fat, when encountered. Forced into an altercation for "self-defense" they are likely to simply fill the area they are in with their poisonous gas -to which they are immune, of course- like, blow it all around themselves, not a ranged cloud, to simply kill everything immediately around/close to them. Sloth, of course, is not stupid, and they will make every decision to their best advantage, as long as it is efficient, deadly, "easy/least effort."
Blacks: Some of the most dangerous draconic creatures to be encountered. Not just because of their sinister cunning and acid breath, but because of their inimical attitude toward creation. There is a literal and metaphoric "darkness" to the black dragons that many of the other chromatics lack. There is a portion of their psyche that is all too well aware of their former greatness, their fall into tainted evil, the perversion of their creation...and they despise creation for it. They are driven, at nearly all times -for territory, for wealth, to the sadistic joy they gain from inflicting harm- by Envy. They are consumed, and consume their surroundings with the withering putrescence of jealous anger. "Taking creation away from others/living creation" is their only solace. So, yes, they are all about the swamps. Guardians and agents of entropy and decay. Necromancy is their preferred magical talents. Moving into a flourishing natural place (like the spring of great river or untouched flowering field, and corrupting it into a putrid shadow of deadly decaying marsh and moor is a black's greatest joy. To the goodly peoples and nations of the world, the arrival and influence of a black dragon to the area may not be immediately known, but the curse and blight they bring with them will be noticed soon enough.
Whites: the most feral and "de-volved" of dragonkind inhabit the frozen wastes of the north and glacial mountain valleys of the world's harshest ranges. A true "speaking, spellcasting" white dragon would have to be ancient and there is no known creature existing -or harassing a populated land- in the last hundred years. Instead, most white dragons are notably smaller than others of their kind. Body size/height rarely topping the size of a dire wolf or horse. Of course, the long neck, tail and broad wings make the creatures seem significantly larger. It is not uncommon for them to be kept and trained as guard animals by the frost giants in the giant lands of the "great white north" beyond the world's northernmost mountains. Within the tundra steppes of the barbarian clans, white dragons typically form into packs and hunt in groups. Fallen into the most visceral of urges, they exist in a state of perpetual Gluttony. Always hunting. Always driven by a "starvation" for something they instinctually know they lost and they can never sate. Always seeking to consume all living things they find and scour the landscapes they pass in vicious cold and cutting ice. While generally considered the "weakest" and "least" of all [true] dragonkind, finding oneself hounded by a pack of whites on the great frozen expanses of the northlands is not something many have survived to tell.
SO, yeah. Little tweaks to canonic lore. But, more or less, the great wyrms we've all known and loved.
