German pediatrician and psychologist Hedwig von Restorff identified this in 1933 memory experiments. A single item that looks different among identical peers draws attention and is recalled far more often afterward.
Colouring only the "recommended" plan differently on a pricing table, or badging just the newest item in a list, are direct applications. But highlight everything and nothing stands out (see: visual-hierarchy) — limit isolation to one thing per screen.
The attention dot below keeps returning to the one differently-coloured circle among the grey ones, and only that circle keeps its memory checkmark.
When to use
Use it when you need "don't miss this one" — a recommended pricing tier, a new item in a list. Limit it to one per screen.