If you want DiceBear to dynamically change colors in your avatar, you have to create the colors in Figma as locale style. Arrange the colors in groups. Name them according to the following pattern: <group>/<option-name>. For example, skin/light.
You will use the locale styles later to colorize paths. DiceBear will then change the colors of the paths within a group depending on the seed and color settings. For the names of <group> and <option-name> you can use alphanumeric characters as well as hyphens.
In the following example you can see how this could look like: