Anyway! I was surprised to see how many people were on the island killing dinosaurs. Are they part of a rep grind or something? It took a while to find a direhorn that wasn't being slaughtered.
I ended up taming one of each color so I could compare. Red and blue were abandoned almost immediately; green was abandoned shortly after. The two I had the hardest time deciding between were brown and white. Brown has more color variety to me, in that it has green eyes and gray plating, etc. The white, on the other hand, looks a little more monochromatic.
However, it wasn't until I went to Darnassus to see them in other lighting that I was finally able to decide. I had been slightly leaning towards the white, because I just had a feeling about it, but seeing it in the temple there cemented it.

I haven't come up with a name yet, but I'm toying with Xanthic (means something having a yellowish color). I'm sure something will come to me.