SIAM. THE CAPRICORN BIRTHSTONE COLOR IS SAID TO KEEP THE WEARER SAFE DURING TRAVEL. Those born in January, or under the star sign of the goat, have Siam as their birthstone color. Its deep red color changes under different light sources, just as Capricorns modify their behavior to get ahead. Those who want to improve their status, boost their self-esteem, or even invite romance, will benefit from wearing rich Siam. It symbolizes faith, love and courage, and its properties are said to help build energy levels and prevent nightmares in children.