How to use the @microsoft/fast-colors.ColorRGBA64 function in @microsoft/fast-colors

yOffsetMultiplier,
            opacity,
            blurMultiplier,
            blurBase = 0,
        }: ShadowConfig = shadowConfig;
        // TODO: (Breaking) Remove default https://github.com/microsoft/fast-dna/issues/2469

        const lum: number = rgbToRelativeLuminance(
            parseColorString(backgroundColor(config))
        );
        const opacityMultiple: number = 2 - lum; // white (1) = 1; black (0) = 2;
        return [xOffsetMultiplier, yOffsetMultiplier]
            .map((val: number) => parseFloat((val * elevationValue).toFixed(1)))
            .concat(blurBase + blurMultiplier * elevationValue)
            .map(toPx)
            .concat(new ColorRGBA64(r, g, b, opacity * opacityMultiple).toStringWebRGBA())
            .join(" ");
    };
}

export function applyAcrylicMaterial(
    backgroundColor: string,
    opacity: number,
    fallbackOpacity: number = 0.9,
    topHighlight: boolean = false
): CSSRules {
    const background: ColorRGBA64 = parseColorString(backgroundColor);
    const acrylicConfig: AcrylicConfig = {
        textureImage: acrylicNoise,
        backgroundColor: new ColorRGBA64(
            background.r,
            background.g,
            background.b,
            opacity
        ).toStringWebRGBA(),
        fallbackBackgroundColor: new ColorRGBA64(
            background.r,
            background.g,
            background.b,
            fallbackOpacity
        ).toStringWebRGBA(),
    };

    return {
        "border-top": topHighlight
            ? `${toPx(1)} solid ${new ColorRGBA64(
                  background.r,
                  background.g,
                  background.b,
                  0.1
              ).toStringWebRGBA()}`
            : "",

const darkNeutralLayerL4: DesignSystemResolver = (
    designSystem: DesignSystem
): number => {
    const darkLum: number = 0.14;
    const darkColor: ColorRGBA64 = new ColorRGBA64(darkLum, darkLum, darkLum, 1);
    const darkRefIndex: number = findClosestSwatchIndex(
        PaletteType.neutral,
        darkColor.toStringHexRGB()
    )(designSystem);
    return darkRefIndex;
};

export function applyAcrylicMaterial(
    backgroundColor: string,
    opacity: number,
    fallbackOpacity: number = 0.9,
    topHighlight: boolean = false
): CSSRules {
    const background: ColorRGBA64 = parseColorString(backgroundColor);
    const acrylicConfig: AcrylicConfig = {
        textureImage: acrylicNoise,
        backgroundColor: new ColorRGBA64(
            background.r,
            background.g,
            background.b,
            opacity
        ).toStringWebRGBA(),
        fallbackBackgroundColor: new ColorRGBA64(
            background.r,
            background.g,
            background.b,
            fallbackOpacity
        ).toStringWebRGBA(),
    };

    return {
        "border-top": topHighlight
            ? `${toPx(1)} solid ${new ColorRGBA64(

background.r,
            background.g,
            background.b,
            opacity
        ).toStringWebRGBA(),
        fallbackBackgroundColor: new ColorRGBA64(
            background.r,
            background.g,
            background.b,
            fallbackOpacity
        ).toStringWebRGBA(),
    };

    return {
        "border-top": topHighlight
            ? `${toPx(1)} solid ${new ColorRGBA64(
                  background.r,
                  background.g,
                  background.b,
                  0.1
              ).toStringWebRGBA()}`
            : "",
        ...applyAcrylic(acrylicConfig),
    };
}