Use opacity() CSS function that applies transparency to the samples in the input element. There is an alternative Opacity utility you can use instead.
backdrop-opacity-0
backdrop-opacity-5
backdrop-opacity-10
backdrop-opacity-20
backdrop-opacity-25
backdrop-opacity-30
backdrop-opacity-40
backdrop-opacity-50
backdrop-opacity-60
backdrop-opacity-70
backdrop-opacity-75
backdrop-opacity-80
backdrop-opacity-90
backdrop-opacity-95
backdrop-opacity-100