Do I need more than one trial?

No! If you are comfortable with how you looked at the trial, then you are good to go. I always tell my brides that I will tweak the makeup, if need be, based on my notes when we do the makeup that day. On the day, I am seeing you in the dress, with hair and in the setting of the venue, and I can fine tune if the look needs more color, definition, etc. However, if you are still unsure after a trial, then definitely do a second. Most artists are happy to do a second retrial complimentary or at a discounted price. A talented makeup artist can do any look, and sometimes were simply misguided by your translation of what you think you like.