With the new Farm comes the Marine Observatory. This is basically like an Underwater Unicorn Island, or any of the other "Harvest, get something, smush enough somethings together, get a critter" buildings. Spirits, Serums, DNA, Gems, Fishscales, whatever, it gives you a chance to pretend you are a Mad Scientest. Which is not a bad gig from what I hear.
So below is a Chart, that shows the order the animals appear, plus the color of fish scale they should give.
|Animal||Color Fish Scale|
So Clearly if you want more of a Specific Color, remove from your Observatory the creatures that give OTHER colors.