> So you're telling me that if your customer wants the button in blue and you want it in yellow, you won't put it in blue?

If I don't feel like making the button blue, I won't. If they don't agree with my decision, they are free to take their business elsewhere.

> If someone else is giving you money, they are your boss.

It is true in some respect, but when you're employed, you only have a single or handful of bosses. When you run a business, you have tens, hundreds, or even thousands of customers. You can say NO to any one of them when the push comes to shove.