Clean!! Pretty much regardless of morph.

I don't even tend to like morphs that are "supposed" to be dirty (ie, pewterbees, cinnabees, granite combos). Just isn't what appeals to me.

In a similar vein, I tend to like "reduced" patterns versus "busy" patterns. (Though I won't necessarily turn down an animal that's super bright and clean, but "busy" )

To me, that's the fun of ball morph breeding: Identify what you like, and breed for that!