title: Change colour of checkboxes in Shiny `checkboxGroupInput`
body: <p>In Shiny is it possible to change the colour of checkboxes from the default blue in the below example?</p>
  
  <pre><code>library("shiny")
  server = function(input, output) {
  
    output$value &lt;- renderPrint({ input$checkGroup })
  
  }
  
  ui = fluidPage(
  
    checkboxGroupInput("checkGroup", label = h3("Checkbox group"), 
                       choices = list("Choice 1" = 1, "Choice 2" = 2, "Choice 3" = 3),
                       selected = 1),
  
  
    hr(),
    fluidRow(column(3, verbatimTextOutput("value")))
  
  )
  
  runApp(list(ui = ui, server = server))
  </code></pre>