User blog comment:B214/Question and Answers 6/@comment-9595671-20160820194143/@comment-3435913-20160821001906

赤竜帝 (せきりゅうてい, Sekiryuutei, lit., Red Dragon Emperor)

白竜皇 (はくりゅうこう, Hakuryuukou, lit., White Dragon Emperor)

赤 (あか, Aka) means Red, also pronounced (せき, Seki). The character used in the "Vermilion Bird [of the South]" is 朱 (す, Su, also pronounced Aka as well) which means Vermilion primarily, but also Red, Crimson, Cinnabar and Scarlet.

白 (しろ, Shiro) means White, also pronounced (はく, Haku). The character is the same in the "White Tiger [of the West]", but pronounced (びゃく, Byaku).

黒 (くろ, Kuro) means "Black", also pronounced (こく, Koku). The character used in the "Black Tortoise [of the North]" is 玄 (げん, Gen, also pronounced Kuro as well) which roughly means occultness or mysterious, so has been used essentially on par with black.

青 (あお, Ao) means "Blue" (plus traditional Green), also pronounced many names, but the most prominent being (せい, Sei), as in Seiryuu aka "Azure Dragon [of the East]".

竜 is a simplified version of the still usable 龍 (りゅう, Ryuu) which can also be pronounced (りょう, Ryou) and (たつ, Tatsu)

皇帝 (こうてい, Koutei) is the word for emperor, but both characters can be used desperately to mean the same thing. Other characters include 帝王 (ていおう, Teiou, with 王 meaning "King") and 天皇 (てんのう, Tennou, with 天 meaning Heaven).

I hope this is of some help.