Probably a dark blue, maybe navy. I guess theres lots of good colors like yellow or green its just finding a good speedo in those colors is harder unless youre willing to spend $$ on some premium brand that may or may not sell in your country.
I dont know about you guys but when i look up Speedo material from other guys on the internet i specifically look for a speedo bulge. Doesnt have to necessarily be a hardon but those are most welcome. I also like cockrings behind swimwear and speedo cums but those are rare. What do you look for?