My plants have been growing in about half a day of sun without any particular issues (in our mild climate). They seem tolerant of direct overhead sun as long as they get some protection for half the day. The colors are definitely better in the sun.
I do restart mine every couple years maybe as the rosette gets smaller atop the stem. When I root cuttings I leave them outdoors in bright shade, a little morning sun maybe, until there is a visible sign that they are growing again. At that point more morning sun or 50% shade maybe, with gradual adjustments over the course of weeks to months until the young plant can handle a full daily dose of direct sun. You have to baby them when they are little (esp. leaf propagations) but always try to give strong light, never leave them in deep shade. To some extent the plant tells you how it is dealing with the exposure. When it loses the black color it needs more light.
You can grow one of these as an indoor plant but that requires hours of daily sun (an unobstructed south-facing window is great for overwintering). Reflected light indoors is no good on its own. Given these plants can be a little sensitive to too much sun, they are even more sensitive to too little sun. The happy middle ground is where I try to put them.
Is there something about how you are watering or feeding maybe? Or some other aspect of their care?
