You need the top 10 values to appear in a different color.

Select the lop 10 bars, create a set. and then drag the set to Color on the Marks card.

Create a group field that groups the top 10 values into one group and the rest of the values into another group. Drag the group field to Color on the Marks card.

Select the top 10 bars, and then change the color by selecting Color on the Marks card.

Create a set that has a top 10 condition, and then drag the set to Color on the Marks card.