@atlaskit/adf-schema/dist/es2019/utils/expand-shorthand-hex.js

Shared package that contains the ADF-schema (json) and ProseMirror node/mark specs

const SHORTHAND_HEX_REGEX = /^#?([a-f\d])([a-f\d])([a-f\d])$/iu;
export const expandShorthandHex = input => input.replace(SHORTHAND_HEX_REGEX, (_m, r, g, b) => r + r + g + g + b + b);