Some might mistake their biggest resource as wealth, but the trader's guild's biggest resource is connection. They benefit from connecting other circles and managing the flow of goods and services everywhere. Networking, politics, taxes, policy, and law are all facets of the trader's guild.
Members are often familiar with caravans and trade goods, or are involved with politics. The trader's guild also includes artisans and crafters-- these members create any number of items and art from pottery to charms. Members also tend to be those involved in gathering raw materials. Traders often request protection in the wilds from those in the Mercenary's guild, and fulfill requests of weapons, armor, and other objects in return. Many members are also involved with scholars, as knowledge can translate into connections.
These are examples of appropriate colors for a circle of the Trader's guild.