如何在R闪亮的selectizeInput组标题中设置字体颜色？

library(shiny)

ui <- fluidPage(
  tags$head(
    tags$style(
      HTML("
        .selectize-group-header {
          color: red; /* 设置字体颜色为红色 */
        }
      ")
    )
  ),
  
  selectizeInput(
    inputId = "myselect",
    label = "Select an option",
    choices = list(
      "Group 1" = c("Option 1", "Option 2", "Option 3"),
      "Group 2" = c("Option 4", "Option 5", "Option 6")
    ),
    options = list(
      plugins = list("remove_button"),
      optgroups = list(
        "Group 1",
        "Group 2"
      )
    )
  )
)

server <- function(input, output) {
  
}

shinyApp(ui, server)