The leaves of the Tricolor Ginger (Stromanthe sanguinea 'Triostar') tend to follow a daily pattern. As the morning begins, the leaves are scattered and widespread (similar to one's hair upon first arising).
A couple of hours later, as the day heats up, some of the leaves have started to curl slightly, showing more of their purple undersides.
By early afternoon, the leaves are showing more curl and several have begun to lift themselves up.
By the time evening approaches and the sun starts to set, the leaves have stretched upwards as far as they can reach, showing much of their purple undersides.
During the evening, the leaves will again lower themselves and uncurl, ready to start the entire cycle again the next day. Makes for a rather fun show.