The new alpha value standard rgb() and rgba() functions
The new syntax is to use three values without commas followed by a slash and the alpha channel of the color as a percentage.
Consider the following example of a slightly-transparent blue:
Don't
background-color: rgba(0, 0, 255, 0.8);Do
background-color: rgb(0 0 100% / 80%);
Warning
At the time of writing, in scss (sass), not css, the rgb() will throw a compilation error like this:
Function rgb is missing argument ...