Trilium/apps/client/src/services/css_class_manager.ts

const registeredClasses = new Set<string>();

function createClassForColor(color: string | null) {
    if (!color?.trim()) {
        return "";
    }

    const normalizedColorName = color.replace(/[^a-z0-9]/gi, "");

    if (!normalizedColorName.trim()) {
        return "";
    }

    const className = `color-${normalizedColorName}`;

    if (!registeredClasses.has(className)) {
        // make the active fancytree selector more specific than the normal color setting
        $("head").append(`<style>.${className}, span.fancytree-active.${className} { color: ${color} !important; }</style>`);

        registeredClasses.add(className);
    }

    return className;
}

export default {
    createClassForColor
};