Succulents come in a wide range of colors, and the same plant can even look different at different times of the year. Seasonal color patterns vary greatly, but many varieties show red hues in winter or summer.
Red tones can also be a sign that a succulent is "beautifully stressed". The stress could be from sun exposure, a water shortage, or cold temperatures. Succulents are well-adapted to tolerate sun, drought, and a range of temperatures, so stress coloration does not mean a plant has been damaged, just that it's nearing the limits of its tolerance. Normal colors will return when the stress diminishes.