As a general rule I don't try to sex anything under 5-1/2" as it's just too iffy. I have found that the differences in the urogenital openings are pretty consistent year round, even outside of the breeding season. The two things I look for are the coloration and size of coloration on the ear tab, then I check the urogenital opening to see if it matches.
Males have a larger and darker red coloration on the ear tab and the urogenital opening is almost the same size as the anal opening.
Females have a more orange and slightly smaller coloration on the ear tab and the urogenital opening is noticeably larger than than the anal opening, even outside the breeding season.
Every once in while I will catch a smaller one that doesn't quite match either or but most of the time it is very consistent.
