Determining an outfit as business casual is not easy, but determining if the outfit is professional is kind of easy. Professional is a style that is reserved for more formal business settings, like high-level internal meetings and business liaison ventures.
This style essentially boils down to the traditional suit-and-tie combination with a solid-color dress shirt. It’s best to stick with neutral colors like blue, black, grey, and brown, and footwear should match but remain conservative. It’s all about being casual around your place of business.
Anything other than the traditional clothing falls under the business casual outfit category. This can include a much broader range of options than professional attire, and depending on the company. It can be a problem if you really don’t know the presentation of an event. It’s better to start at the higher end and work your way down to something a little less professional if necessary, but you don’t want to show up on the first day looking like a bum. Try a blazer and pants that aren’t monochromatic, and don’t be afraid to wear a tie or even a vest, but don’t feel limited to solid color dress shirts.
For winter, tailored sweaters should be fine for men in a business casual setting when paired with a collared shirt. Colors for business casual attire should avoid anything overly bright, better if they are monochrome. It’s best to sprinkle such variety in through accessories like pocket squares, cufflinks, a belt, and even suspenders with the right outfit. Be careful not to overdo it with add-ons, since too many will draw unwanted attention. It’s all about balance and aesthetic.
Here’s an article that would help you arrange some outfits on your knowledge.
Here’s an article of ours that should help you with style rules that you should always follow.