Water Marbling with multiple colors can be a big pain to do but, at the same time the results can be fun and unique. Recreating an exact pattern takes a lot of skill but many patterns can be accomplished with practice.
Likewise, the saturation or opacity of the color can vary depending on the brand and finish of the polish. I've also found that shimmers retain their finish but provide very little coverage. As I've mentioned before creme finishes are my favorite, and 4/5 colors used were cremes.