Both define the same colors, but Hex uses a hexadecimal string like #FF6550 while RGB/RGBA lists decimal channel values, e.g. rgb(255, 101, 80). RGBA adds a fourth alpha value for opacity, such as rgba(255, 101, 80, 0.4).
Use the RGBA format and set the alpha value between 0 (fully transparent) and 1 (fully opaque). For example, rgba(255, 101, 80, 0.4) renders the color at 40% opacity. You can adjust the Opacity (Alpha) slider here to preview it.
Yes, modern browsers support 8-digit Hex with an alpha channel, such as #FF6550CC, and 4-digit shorthand like #F65C. For broad legacy support, RGBA remains the safest way to express opacity.
RGBA has been supported in every modern browser for years, including all current versions of Chrome, Firefox, Safari, and Edge. Only very old browsers like Internet Explorer 8 and earlier lack support.