__ Dash, My Little Pony With a Spectrum Tail
Puzzle 5 of Famous Horses Hard Pack
Question is: __ Dash, My Little Pony With a Spectrum Tail
and the answer is: RAINBOW
Word Meaning:
RAINBOW — A multicoloured arch in the sky, produced by prismatic refraction of light within droplets of rain in the air.
Definitions from Wiktionary.