There must obviously be two loops, jQuery can't perform magic. The first .css() call will iterate over the cached array of elements, apply the color attributes

There must obviously be two loops, jQuery can't perform magic. The first .css() call will iterate over the cached array of elements, apply the color attributes and then return a reference to the jQuery instance. The second call will loop once again and this time apply the font-size attribute. There is no extra DOM lookups, but there will certainly be two loops.