Same as color name "Tomato":

rgb(255, 99, 71)

#ff6347

hsl(9, 100%, 64%)

Same as color name "Tomato", but 50% transparent:

rgba(255, 99, 71, 0.5)

hsla(9, 100%, 64%, 0.5)

In addition to the predefined color names, colors can be specified using RGB, HEX, HSL, or even transparent colors using RGBA or HSLA color values.

The inline styles used on this page

<h1 style="background-color:rgb(255, 99, 71);">
<h1 style="background-color:#ff6347;">
<h1 style="background-color:hsl(9, 100%, 64%);">
<h1 style="background-color:rgba(255, 99, 71, 0.5);">
<h1 style="background-color:hsla(9, 100%, 64%, 0.5);">