OpenType-SVG is a font format in which an OpenType font has all or just some of its glyphs represented as SVG (scalable vector graphics) artwork. This allows the display of multiple colors and gradients in a single glyph. Because of these features, we also refer to OpenType-SVG fonts as “color fonts”.
Back in March, Roel Nieskens wrote about his experience building a color font and described the problem that they intend to solve:
Typography on the web is in single color: characters are either black or red, never black and red.