Most major corporations have uniform policies in place. The strictness of these policies varies from company to company, but even the least strict of these policies request that their employees at least wear a single item with the company colors. But for quite a few employees, such a request can simply not seen as a simple request as their company owns a majority stake of their shares. Although there is no hard "rule" that enforces it, uniform rules tend to grow more and more strict the fewer shares of themselves an employee owns. It's not uncommon for companies to enforce dress codes to their Vassals even outside of working hours.
But even in companies with less strict dress codes, there is quite a bit of pressure to conform to the company style.