MultColorLerp

public static Color MultColorLerp(float t, params Color[] colors) {
    if(colors.Length < 2)
        throw new System.ArgumentException("Need at least 2 colors");

    if(t < 0f)
        return colors[0];
    else if(t >= 1f)
        return colors[colors.Length - 1];

    var i = (int)(t * (colors.Length - 1));
    return Color.Lerp(colors[i++], colors[i], Mathf.Repeat(t * (colors.Length - 1f), 1f));
}