I don't see anything wrong with caring about style, especially for a younger person. There is a bit of an ethos that if you are going really flashy you ought to be a good skier first, though, at least among us old guys. And style should be in addition to function, not in place of it. I did see a lot more bright colors last year than I remember from prior years.
For fashion questions, it would be good to lead with info about your age and whether you are male or female.
For helmets, the important info is head circumference and round or oval skull shape. I bought my helmet on-line when I couldn't find any that were big enough in the stores, but the site I went to was a helmet-specific one with detailed measuring instructions.
My own sense of style (at 55 years old, male, probably irrelevant to you, but hey....) is that dark pants, a sold color jacket in an attractive bright color, and matching helmet would be really sharp. But the colors need to exactly match. The blue/yellow combos look good to me too, but I probably wouldn't wear it myself.