Duotone icon.
A two-layer icon: a filled silhouette at low opacity plus a stroked detail layer, both `currentColor`. The icon inherits its hue from the parent, and a per-item hue is allowed here — the only sanctioned multi-colour element.
When to use
Section and feature icons that want a touch of depth without going full multi-colour. Set the hue on the parent (or the svg itself) so a row of icons can each carry a different role colour — a box in accent, a doc in positive, a bolt in cobalt. Reach for a single-layer stroked icon when the glyph is too small for the fill to read (≤16px).
One svg, two layers — a filled silhouette at low opacity plus a stroked detail, both currentColor. The hue is set per item with color on the svg, so each icon carries a different role colour while staying themeable.