Dark Cymbal

Most describe light and dark as a sound characteristic.
Light cymbals are most predominantly used in Jazz, and dark cymbals in Rock styles. But there are No Rules.
Colors range from extreme dull finish to a mirror finish for all cymbals, this is a personal preference of how clean you want your cymbals.
The more clean, the more "shimmer" the sound.
The more dull, it "mellows" the sound a little.
Cymbals will mellow with age regardless, some drummers only buy used cymbals for this reason.
The weight of the cymbal will give you an idea of the sound. heavy, light, and in between.