Element of many signs

NEON

This glowing gas lights up storefronts and gives off a bright red-orange hue.

This clue plays on the double meaning of "signs." In one sense, it refers to neon signs—the bright, glowing displays often used in advertising, which are filled with neon gas. In another, it hints at the chemical element itself (neon, or Ne on the periodic table), which is commonly used in those signs. The word "many" suggests neon is a widespread or familiar element in both contexts.