Dragon Types
On Akavir, the Tsaesci attempted to "consume" the black dragons, and drove the dragons to the Empire of Po Tun. This led to a war between the Ka'Po'Tun's and the Tsaesci. During that war The Tsaesci killed most of the dragons. Black Dragons have a dark gray skin, are considered to be the lowest Dragon and use almost exclusively Yol (fire). In The Elder Scrolls V: Skyrim, they are the first type of dragon encountered by the player.
Blood Dragons
Blood dragons are recognized by their greenish-gray skin, crowned head, and large fan formation on the end of their tail. They can use Yol (fire) or Fo (frost) breath attacks. In The Elder Scrolls V: Skyrim, they will start to spawn around level 15.
Frost Dragons
Frost dragons have a shiny white skin with massive protruding black spikes coming out of their back and predominately use Fo (frost) breath that deals damage, slows the player down, and reduces stamina. In The Elder Scrolls V: Skyrim, they can be encountered after hitting level 20.
Elder Dragon
Elder dragons have a bronze skin and use Yol (fire) or Fo (frost) breath attacks. They have a large amount of health and are considered some of the strongest dragons, only surpassed by the Ancient Dragons. The Elder Dragon's attacks are generally strong and debilitating. In The Elder Scrolls V: Skyrim, they can be encountered after hitting level 23.
Ancient Dragons
Ancient dragons feature red skin with black markings and spikes. They are considered as one of the strongest type of dragons and use Yol (fire) breath or Fo (frost). They also have the ability to use Unrelenting Force on the Dragonborn. In The Elder Scrolls V: Skyrim, Ancient Dragons are encountered after approximately level 30 and they become the predominant Dragon of Random Encounters in the very late levels.
Red Dragon
Red dragons feature red skin with black markings and spikes. They are considered one of the strongest type of dragons and use Yol (fire) breath. Only two red dragons are known, Nafaalilargus, a mercenary in the employ of Tiber Septim during his conquest of Tamriel, and Odahviing, the right-hand of Alduin. In The Elder Scrolls V: Skyrim, Odahviing is encountered during the main quest.
Skeletal Dragons
Skeletal dragons are usually encountered in dungeons, caves, and any underground structure with draconic lore in Skyrim. Although flightless and not having dragon souls, they are still dangerous. InThe Elder Scrolls V: Skyrim, one such dragon appears insideLabyrinthian, an event encounter during the Staff of Magnus quest.
Green Dragon
The Green dragon is very rare and features green skin. Therefore i do not have any pictures of one cause only one green dragon is known: Skakmat, Nulfaga's dragon familiar. Its most famous feat was, under Nulfaga's orders, the attempted stoppage of the Battle of Cryngaine Field by creating a sudden unnatural fog which blinded the combatants. When the mist cleared, it was found that Lysandus' heart had been pierced by an arrow fired blindly by one of Sentinel's archers, fulfilling the prophecy which had foretold his death during the battle. Also, the Daedric Prince Peryite takes the appearance of a green dragon. Blood Dragons with their dark green coloration are popularly believed to be of this type of dragon.