I am trying to change the colour of a button using css in R Shiny. The default bootstrap styling seems to colour the button light grey when it is pressed (i.e. **during** the click), but I want it to be green. I believe this is done with the `:active` pseudo-class selector but it doesn't work: the button is still light grey when depressed but the lime colouring of the button does work.

ui.R

```
ui <- fluidPage(
        theme = "style.css",
        actionButton("my-button", "Click me")
    )

```

style.css

```
.btn, .btn:hover {
  background-color: lime;
}

.btn:active {
  background-color: green;
}

```