The random() function in CSS is an experimental feature (i.e., not supported in any browser) that returns a random numeric […]

.element { width: random(5rem, 25rem, by 5rem); }

The CSS rgb() color function represents color in the sRGB color space specifying their redness (r), greenness (g), and blueness (b), and an optional transparency value.

.element { color: rgb(0 0 0 / 0.5); }