Cactus flowers

When I bought the Christmas cactus a few years ago, it was only fist size. It keeps growing over the years. Now there are two plants spreading out and the green clay pot is no longer large enough to hold them. Every year in January or February, they give a few flowers, not too many, not overly crowded, just a few to light up the room. The buds were bright purple and but when they bloomed, the color turned to scarlet.