means Full of energy, brightness, and life — whether in color, sound, mood, or personality.

from From Latin vibrantem, the present participle of vibrare, "to shake, quiver, set in tremulous motion" — the same root that gives us vibrate and vibration. A vibrant thing was originally one that quivered with motion, like a plucked string still trembling; over time that literal shimmer became the figurative shimmer of energy and intensity we mean today.