指示器的颜色由NavigationBarItem中的**indicatorColor**属性定义。
要删除它，您必须应用与NavigationBar相同的containerColor。
如果使用默认值（containerColor = surface颜色），则必须计算应用于containerColor的不同高程处的表面色调颜色。
类似于：

NavigationBarItem(
    icon = { androidx.compose.material3.Icon(Icons.Filled.Favorite, contentDescription = item) },
    label = { androidx.compose.material3.Text(item) },
    selected = selectedItem == index,
    onClick = { selectedItem = index },
    colors = androidx.compose.material3.NavigationBarItemDefaults
        .colors(
            selectedIconColor = Red,
            indicatorColor = MaterialTheme.colorScheme.surfaceColorAtElevation(LocalAbsoluteTonalElevation.current) 
        )
)

在其他情况下只使用相同的颜色：

NavigationBar(
    containerColor = Yellow
){

    items.forEachIndexed { index, item ->
        NavigationBarItem(
            icon = { androidx.compose.material3.Icon(Icons.Filled.Favorite, contentDescription = item) },
            label = { androidx.compose.material3.Text(item) },
            selected = selectedItem == index,
            onClick = { selectedItem = index },
            colors = androidx.compose.material3.NavigationBarItemDefaults
                .colors(
                    selectedIconColor = Red,
                    indicatorColor = Yellow )
        )
    }
}