You said: "if its not something reusable or does not contain more than 2 styles"
I would add another reason to use external stylesheets: maintainability. If you (or someone else) has to fix your code in the future, you will have a much easier time of it if all of your styling is in one place. You will not remember that you added that little bit of styling inline, and you may spend hours hunting for it.
It is a good standard to keep all styling separate to maintain clean, maintainable code.
That said, we can acknowledge that it is "ok" to use inline styles, as you asked in your question. However, best practice is often something more than "ok" and should serve as a guide as often as possible.
