According to wikipedia:

The exact nature of chemicals that make Jovian zones and bands so colorful is not known, but they may include complicated compounds of sulfur, phosphorus and carbon.

Liquid ammonium hydrosulfide, for instance, is yellow-orange in color; besides direct coloration, even colorless gases scatter different colors of light differentially.

As for the second question, small solid crystals and droplets fall very slowly in a gaseous medium; terrestrial clouds are made of ice crystals and water droplets. I imagine that ammonia crystals would be forming and precipitating in a simultaneous cycle.

According to wikipedia:

The exact nature of chemicals that make Jovian zones and bands so colorful is not known, but they may include complicated compounds of sulfur, phosphorus and carbon.

Liquid ammonium hydrosulfide, for instance, is yellow-orange in color; besides direct coloration, even colorless gases scatter different colors of light differentially.

As for the second question, small solid crystals and droplets fall very slowly in a gaseous medium (and are lifted by updrafts); terrestrial clouds are made of ice crystals and water droplets. I imagine that ammonia crystals would be forming and precipitating in a simultaneous cycle.