How to get more colors for the Custom Designs app in Animal Crossing: New Horizons

If you're looking to spice up your Animal Crossing: New Horizons
wardrobe, and the colors you start with may not cut it for you. Do not
worry, there is a way to get more palettes and even edit each individual color
at your convenience. Here's how.

Obtain
upgrading the Pro Designs app

1. Pay your moving expenses
   When you get to your island, you owe Tom Nook 5000 miles. Earn miles by completing various quests and return 5000.
2. Bring 800 miles to the Nook stop
   Once you have paid your miles, you will have access to Redeem Nook Miles option at Nook Stop. You will need an additional 800 miles to purchase the Pro Designs upgrade for your Custom Designs application.

Screenshot via Nintendo

Once you have the Pro Designs upgrade, which can access the app, you'll have access to new Pro models and a whole slew of new colors.

Palettes

Under tools, with Change palette you can choose what
palette you want to work with, from a selection of 14 different presets
pallets. Each palette offers 15 different colors.

Screenshot via Nintendo

Edition
Mixable

Can't find a predefined color or palette that tickles your fancy? No problem. You can also change the colors individually to get the exact shade you are looking for. With the Change color , you can use 3 different sliders to adjust the color: hue, brightness and brightness.

Screenshot via Nintendo

Since the palettes only have 15 colors, you cannot create
a design that uses more than 15 colors, but each color can be hand selected
in that amount, if you wish.

New
Colors everywhere

These new color options will work regardless of whether you want to create a basic or professional design, so you can use these options to modify designs you've already made, as well as use them for face paint designs, which are not available in the Pro Design Section.

You can use these colors for all future fashion designs.