Hmmm, I am not so sure. The leaves on the majority of macrophyllas tend to turn yellowish in the Fall while a small number, like Lady In Red, etc will resemble oakleaf hydrangea leaves that to turn red/purple/brown-ish colors. The whole leaf should change, not bits or pieces like in your picture.
My concern is on the somewhat circular orange/brown roundish spots that can become large blobs/spots. There is a fungal infection called leaf spot or Cercospora Leaf Spot that looks like that. Also, some of the leaves in the picture (near 3 o'clock and 7-8 o'clock) look grayish... sign of either dust or powdery mildew (PM), yet another fungal infection.
If you can read the information on the link below and confirm that these are fungal infections, I would address them by not doing any overhead watering and instead watering the soil early in the mornings only (5-6am). Watering the leaves usually results in these issues, which become visible now as Fall arrives, chlorophyll production goes down (it masks the leaf spots in prior months) and carotenoid/anthocyanin pigments production goes up. To avoid the spread of these two infections, I dispose the dried out leaves in the trash and, in "bad" years, I replace the mulch as well.
There are some fungicides that you can use for leaf spot but they cost a lot and they only help control it, not cure it. Your leaves are about to dry out soon so it is hard to decide whether to buy fungicides for Cercospora or not but, if you buy, you could start applying fungicides for leaf spot by next year's summer. I have some old macs with Cercospora that I control with drip irrigation and disposing of dead leaves.
For PM, good air circulation, which this plant appears to have, also helps. PM remedies that you can try: (1) 1 tbsp of baking soda + 1 tsp hort oil (or liquid soap) + 1 gallon of water (this solution is more of a preventative measure than a cure); (2) same as before but replace baking soda by potassium bicarbonate; (3) 1 part milk to 9 parts water (or a stronger solution like 1 milk to 2 water) or (4) apply neem oil according to label directions. Or commercial fungicides of course.