Change the screen color when opa set to 0

How-to
1

Hello all,

Version: Lvgl V8.3

The screen display white when I set “lv_scr_act()” layer opa to 0%.
lv_obj_set_style_opa(lv_scr_act(), 0, NULL);

Now, how can I change this white color to black when I set opa to 0%?