Tree Diagram Configuration.

Anonymous , Power Bi conditional formatting is not supported with once you use details in tree map.

Move both of them  category expand and the use conditional formatting

color on brand has been used with help measure and field value formatting

Brand Color = Switch( true(),
max('Item'[brand]) = "Brand 1" , "red",
max('Item'[brand]) = "Brand 2" , "blue",
max('Item'[brand]) = "Brand 3" , "green",
max('Item'[brand]) = "Brand 4" , "gray",
max('Item'[brand]) = "Brand 5" , "yellow",
max('Item'[brand]) = "Brand 6" , "orange",
max('Item'[brand]) = "Brand 7" , "brown",
max('Item'[brand]) = "Brand 8" , "Cyan",
max('Item'[brand]) = "Brand 9" , "Tan",
max('Item'[brand]) = "Brand 10" , "Violet",
max('Item'[brand]) = "Brand 11" , "Gold",
"silver"
)

How to do conditional formatting by measure and apply it on pie?
https://www.youtube.com/watch?v=RqBb5eBf_I4&list=PLPaNVDMhUXGYo50Ajmr4SgSV9HIQLxc8L
https://community.powerbi.com/t5/Community-Blog/Power-BI-Conditional-formatting-the-Pie-Visual/ba-p/1682539
https://amitchandak.medium.com/power-bi-where-is-the-conditional-formatting-option-in-new-format-pane-66e0afcb15f3

How do you have the cells that from the same brand close to each other.