Always a big turn on for me when I see a guy wearing somewhat sheer white shorts and you can see his underwear through his shorts. I'm equal opportunity - white briefs, striped boxers, red boxerbriefs - I always love to see it all.
For me, the best part is when I can see the distinct outline of the front panel of the guy's white briefs with the seams of the fly totally visible. I was at a pizza buffet place and saw a group of young guys who came in after playing sports. The one guy in white mesh shorts made my jaw drop. I could see every detail of his briefs, front and rear, as though he wasn't wearing the mesh shorts. It was very distracting as I could not stop looking at him every time that he went to the serving line. His briefs had become stretched out from whatever sport they had just played, and I could see the outline of his big, soft dick loosely pointing straight down between the seams in the fly. Of course, when I returned home, I had to rub one out thinking about how the bro sported his white briefs for everyone to see.