rgba(170, 0, 0, 0.8)

Every CSS color system has an optional alpha component that can define a color’s level of transparency. For example, to produce a background color of red that is halfway transparent for a <div> with an id of genera, we could write:

white#fffefc
pearl#fbfcf7
alabaster#fefaf0
snow#f4fefd
ivory#fef7e5
cream#fffbda
eggshell#fef9e3
cotton#fbfcf7
chiffon#fafaf1
salt#f8efec
lace#faf3ea
coconut#fff1e6
linen#f2ebd3
bone#e7dfcc
porcelain#fffffc
parchment#fcf6df
rice#fbf6ef

The CSS named color system is notoriously bad: keywords are often difficult to remember (navajowhite), illogical (darkgrey actually displays lighter than dimgray) and/or visually questionable (lime and fuchsia verge on the bilious).

Until CSS custom named hues and variables are widely supported, preprocessors remain the best way to create your own custom color names. Defining site colors in Sass creates a cohesive color library that can be used to style content quickly and easily, with named colors that are significantly easier to remember and type than their hex equivalents. However, it can be burdensome to build a decent color library with a logical naming system.