The colors follow Gameday's pitch identification algorithm. I think it's fairly clear that Gameday is miscategorizing some of Mejia's changeups as two-seamers. In fact, all of the pitches that Gameday thinks are two-seamers, I think are changeups. The blue circle are the pitches I think are changeups.
In Mejia's previous start, he did throw a lot of two seamers in the 93 mph range. I've circled what appears to be a cluster of fastballs that could be two seamers although their velocity matches Mejia's other four-seamers. One thing the chart makes clear is both the incredible movement on Mejia's heater, and it's variability. Mejia simply must learn to harness his ability to make the ball move, but do so in a way where he can control it. He's not doing that now.
Lets focus in on the movement on Mejia's offerings. The graph below shows both the horizontal and vertical movement on each of Mejia's pitches. Outside of the two curveballs he threw, the striking thing about the chart to me is that everything else is fairly indistinct.
The take home message for me: there's a lot of velocity (duh!), but everything else needs some work.