How to set the scroll bar track for lvgl8.4?

[FloatingDust]

What MCU/Processor/Board and compiler are you using?

stm32f103rct6/keil

What do you want to achieve?

Set the track of the scroll bar of the list to gray。

What have you tried so far?

Searched the information, and there is no relevant solution.

Code to reproduce Add the relevant code snippets here.