Types of Dragons (Dragonish Translations done myself):
Ved Dova / Black Dragons - Black Dragons are one of the most common in Skyrim, they have a browny/black scales, 2 main horns, a rounded spear-head tail and light brown, webbed wings. They have only been seen using Yol Toor Krein.
Iiz Dova / Frost Dragons - Frost Dragons are slightly less common and more powerful than Black Dragons, they have white/blue scales, 2 main horns, a nose horn, a very spiked back and tail and light blue, torn wings. They mostly use (and possible only use) Iiz Slen Nus.
Yol Dova/ Fire Dragons- Fire Dragons are (probably) just as common as Iiz Dova. They have red/golden scales, 5 main horns, a nose horn, studded back, a spear-head tail and thickly webbed golden/red wings. They mostly (and possibly only use) Yol Toor Krein
Unknown Spined Dragon- These Dragons look to be alot more powerful than other Dragons we have seen up to now, they have brown/golden scales, webbed horns, webbed/spined back, webbed/spined tail and grey/blueish cracked (or veiny) wings. They have only been seen using Tol Yoor Krein
So thats all i've got up to now, if i made a mistake or there's more to be added please inform me ;D