How do I use a custom background in expand icon column

[lianzx3]

How do I use a custom background in expand icon column when I used DataGrid detail hierarchy.

for example:

code:

@using RadzenBlazorDemos.Data
@using RadzenBlazorDemos.Models.Northwind
@using Microsoft.EntityFrameworkCore

@inherits DbContextPage

<RadzenStack Gap="1rem">
    <RadzenDataGrid RowRender="@RowRender" ExpandMode="DataGridExpandMode.Single"
                    Data="@customers" TItem="Customer" CellRender="OnCellRender">
        <Template Context="customer">
            <RadzenDataGrid Data="@customer.Orders">
                <Columns>
                    <RadzenDataGridColumn Property="@nameof(Order.OrderID)" Title="Order ID" />
                </Columns>
            </RadzenDataGrid>
        </Template>
        <Columns>
            <RadzenDataGridColumn Property="@nameof(Customer.CustomerID)" Title="CustomerID" Width="100px" />
            <RadzenDataGridColumn Property="@nameof(Customer.CompanyName)" Title="CompanyName" Width="200px" />
        </Columns>
    </RadzenDataGrid>
</RadzenStack>

@code {    
    IEnumerable<Customer> customers;

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();

        customers = dbContext.Customers.Include("Orders.OrderDetails.Product").Include("Orders.Employee.EmployeeTerritories.Territory.Region").ToList();
    }

    public void OnCellRender(DataGridCellRenderEventArgs<Customer> args)
    {
        args.Attributes.Add(
            "class",
            "rz-background-color-primary-light"
        );
    }
	
    void RowRender(RowRenderEventArgs<Customer> args)
    {
        args.Expandable = args.Data.Orders.Any();
    }
}

[enchev]

Here is an example:

<style type="text/css">
.rz-col-icon {
    background-color: red  !important;
}
</style>