R Shiny：更改tabPanel标题的默认颜色

Question

如果您运行以下代码（取自https://docs.djangoproject.com/fr/2.0/topics/i18n/timezones/），默认情况下“title2”和“title3”将显示为灰色。如何将此默认颜色从灰色更改为例如“白色”？

this question

谢谢。

library(shiny)
library(shinydashboard)

ui <- function(){
  navbarPage(title = 'Hello', 
             tabPanel("title2"),
             tabPanel("title3"),
             tags$head(
               tags$style(type = 'text/css', 
                          HTML('.navbar { background-color: red;}
                               .navbar-default .navbar-brand{color: white;}
                               .tab-panel{ background-color: red; color: white}
                               .navbar-default .navbar-nav > .active > a, 
                               .navbar-default .navbar-nav > .active > a:focus, 
                               .navbar-default .navbar-nav > .active > a:hover {
                               color: #555;
                               background-color: green;
                               }')
                          )
                          )
                          )

}

server <- function(input, output, session){
}

shinyApp(ui = ui, server = server)