Shiny 闪亮的仪表板更改slectInput的背景色

我有一个有多个选择输入的闪亮Dashard。现在，如果单击了默认值之外的值，我想更改selectInput的背景色

下面是一段代码片段：

dbHeader <- dashboardHeader(
  title = "Test",
  titleWidth = "400px"
)

ui <- dashboardPage(
  dbHeader,
  dashboardSidebar(
    uiOutput("filter_head")
  ),
  dashboardBody(
    #some content
  )
)

server <- function(input, output, session) {
output$filter_head <- renderUI({
  column(
      12,
      selectInput("select_1", h3("Select1"),
        c(
          "Default", "A", "B",
          "C",
          "D"
        ), selected = "Default", selectize = FALSE, multiple = F)
      ),
 selectInput("select_2", h3("Select2"),
        c(
          "Default", "A", "B",
          "C",
          "D"
        ), selected = "Default", selectize = FALSE, multiple = F)
      )
)
    })
}
shinyApp(ui, server)

---

dbHeader好的，我知道了。使用uiOutput和if else语句

我创建了一个新的uiOutput元素，并使用render方法中的语句：

uiOutput("style_select_1")      

output$style_select_1<- renderUI({
        if(is.null(input$select_1)){
          return()
        }
        else if(input$select_1!= 'Default'){
          return(tags$style("#select_1{background-color:red;color:white;}"))
        }
      })

ui输出（“样式选择1”）
输出$style\u选择\u 1