In "Total Nightmare", Hiccup thought that Snotlout needed a replacement dragon when Hookfang "ran away'. When Hiccup brought in these three dragons, Snotlout named them after Hookfang and rejected them.
Hookfire, Fangmaster and Hookblazefang are typical looking Monstrous Nightmares that are native to Dragon's Edge, or at least the island. Hookfire and Hookblazefang have very similar coloration, both being light green mixed with yellow. Fangmaster is multi-colored, being pink, blue and yellowish-green.
Fangmaster's colorings resembles those of Hookfang's mate, while both Hookfire and Hookblazefang resemble those of Firescrapes and Whip-Slash.