Hello!
I was wondering which part of the gradient is primary and which one is secondary. Now that I get the point I make you benefit from this little tip ^^
So when you put a Tori stand erect with the right arm up and the left arm down:
- The Primary Gradient is always above the secondary
- The Secondary Gradient is always below the primary
- Feet and left arm's extremities are Secondary Gradient
- Right arm's extremity is Primary Gradient

Example...
Here:

- The Primary Gradient is Chronos
- The Secondary Gradient is Radioactive

the top is primary the bottom is secondary

You can also use the Torishop ingame, and try on items to see wether it's primary or secondary.