The possible values that a Trait can have are Trait Values. They have two properties:
Name: the value name that will be shown in NFT metadata
Rarity: the likelihood that an NFT will have this value in the overall Trait Set or Drop. Rarity is entered as a percentage between zero and one. Ex. 0.5 means 50% of your NFTs will have this value.
The total Rarity of all of the Values in a Trait do not necessarily need to add up to 1. In these instances the remaining percentage will be allocated to a "None" value, which would not correspond to Artwork.
Trait Values can each be entered individually, but you can also Add a List of Values (entered on separate lines) or Import a List of Values by providing them in a comma separated list (CSV file), each line with a value name and then a rarity.
For example, your Colors.csv might be defined as:
When adding a large number of Trait Values as a list, it may also be convenient in some cases to use the Distribute Rarity Evenly option to set a rarity across the entire group of traits at once. Of course, you may opt to give each value its own individual rarity – CSV import may be more convenient in that case.