But I myself actually favor black pants - One, becz I am not usually found in "business" (e.g., corporate) settings even when I am conducting (my) business.
Two, I prefer it precisely for the "severity" it conveys. I find that it works well for me when I wear it with intense rust brown or deep hunter-green sport jackets and dark bronze-tone ties.
But indeed: rules are rules, personal style is personal style. And here, insofar as a "personal style" IS a style (yours), and a "style" is a kind of "language" it too has an obligation to be coherent, lest you "speak" jibberish with your attire. There are no rules except yours, but you must still have them. It's kinda like "diction": the way you speak.
So then, your subjectivity/sense of style has to be refined/disciplined enough to make, and keep, certain rules of your own making.
This mastery of autonomy in creating a personal style is also what refines & strengthens your confidence in your sense of judgment. It takes courage - willing to fail, and make mistakes - and a certain intellectual curiosity about what it means to project an image of yourself to the world.... because, we DO project an image, whether we do it consciously or not. Why not be the master of your own image(s)? After all, you spent a lot of time/money in researching/buying that watch, didn't ya? You'd rather go naked-wrist than wear an INVICTA quartz, wouldn't ya? Well, there ya go.
What you wear - and how it is "appropriate" also has a lot to do with your own character AND line of work - these contextualize the "propriety" of your "style", and make it acceptable or not. (To wit, what Steve Tyler wears is not acceptable on anyone - not even on a woman - but on him.)