Colonial subjects provide their overlord with the following contributions:

2.5% of monthly income from all sources.
Monthly manpower and sailors to reinforce your armies and fleets.
33% of their trade advantage and trade capacity, representing the integration of their markets into your own. (Can be increased by an additional 50% at the cost of 33% subject loyalty).
Loyal colonial subjects will join all offensive and defensive wars of their overlord.
Access to actions such as siphon income and press sailors, giving short boosts of ducats or sailors.

Colonial subjects are not passive entities, either. They possess their own Cabinet and can enact cabinet actions, focusing on local development and control. This makes them semi-autonomous partners within your empire. Useful allies, but also potential rivals if their loyalty is strained.

Although the market of Anace is owned by Portugal’s Colonial Subject, Portugal can still extract their gold and gems to their own home market.

With the new interconnected systems at play in EUV, development in the New World is designed to be a gradual and organic process. Colonies do not instantly transform into bustling cities or economic hubs. Instead, growth unfolds over time, shaped by when and where colonization begins.
Regions that are colonized early will naturally develop earlier, gaining population, infrastructure, and trade connections before their later-settled counterparts. This reflects the historical pace of change, where the earliest colonial footholds became centers of wealth and power, while more remote or less desirable lands lagged behind until much later.