Yes, it is. As the production of chlorophyll (green) goes down in the Fall, you get some different colors showing up on some hydrangea leaves. The usual yellows are common of course but, you can also get some purples, reds, oranges. It's a function of weather, soil minerals, the variety of hydrangea that you have, etc so no guarantee you will always see them exactly the same way, reliably, every year though. Eventually, the leaves and blooms will end brown. Cold weather (frost) that zaps the leaves may speed up the leaves turning brown and skip turning different colors at times. You can deadhead the blooms at any time or keep them for winter interest. If you are located in places that get cold, prepare some winter protection in order to have reliable bloomage in the Spring. The hydrangea you have develops invisible flower buds in July-August near the end of the stems. If it is a rebloomer, it will bloom again in mid-to-late summer. The blooms it has now will fall on their own in the first half of the year. The leaves will disintegrate on their own a few months after they turn brown. Once the stems harden in preparation for winter (oh, fyi, stems may also change colors when hardening), they will leaf out sometime in Spring but, if you do not see leaf out by mid-to-late May 2018 then you can cut the stems all the way down (you should get new stems by then).