Here's some vocabulary for ya, the pimples are called vesicles, and the raised area arouned the mouth is called the hypostome.
Also, at the top of the hypostome on yumas, they have a neon green/yellow ring around the mouth. I've only seen a few ric floridas that have this.
And there's always the way to ID them by experience. After you've seen enough ric fl and yumas, you can distinguish between the two and not even know how you do it.