Answer: This plant does color better in a full sun location, meaning direct sun all day long. But it should turn at least somewhat red in a half day of sun.
Sometimes the color does not develop because the plant is not hardening off enough before the truly cold weather sets in. Most often this happens because they are being generously watered and fertilized too late into the fall.
If you are fertilizing, use only a top dressing of compost and/or a general purpose granular fertilizer per the label directions and apply them once in the spring. If it is adjacent or surrounded by lawn that is being fertilized, do not fertilize the shrubs separately in addition to the lawn. This plant does not need a rich soil or high fertility to grow well.
If you are watering routinely, keep in mind that watering is really only needed if rain is inadequate and that these are quite able to tolerate a dry soil once established -- that is one of the reasons, along with the ability to grow well in just average soil -- they are considered so low maintenance.
You should allow the soil to dry out a bit between deep waterings. To know if you need to water, dig into the soil with your finger. If it is still damp, do not water yet. When you do water, water thoroughly and slowly so it soaks down deep. This is preferred over a daily light watering because it encourages deeper rooting. After you water, wait a few hours and then dig down to see how far the water went; sometimes it can be surprising.
It may be too late for this season, but I hope this helps for next year.
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