The Silver Saints are the middle class among Athena's Saints. They have better knowledge of Cosmo than the Bronze Saints, being able to launch attacks at a speed between Mach 2 and Mach 5, but they are still no match for a Gold Saint. The Silver Cloths cover more of the body than a Bronze Cloth, and freeze at -200 degrees.
The Silver Saints are the middle line between Bronze and Gold Saints, and are mostly sent out on missions in groups of five, acompanied by one or two Gold Saints and ten Bronze Saints, most likely.
Even though they are Silver Saints, in the anime, not all Silver Cloths share the same silver color.