The 18 figures are made by Kid Designs, and are sold singly in blister packs. They range in size from 1.75 to 2 inches, depending on how extended their antennae are. They are made of a medium-hard, semi-pliable plastic that is common to many figures. While they lack any articulation, the plastic and paint is top quality. They cost $4 each.
The default "mood" of a Boov corresponds to either purple or pink. Here is what we learn about their emotional states based on the 15 colored Boov figures:
Blue = Doubtful or Sad
Green = Naughty or Grumpy
Yellow = Shocked or Frightened
Orange = Excited or Silly
Red = Angry (only one figure)
Bright Pink = Bashful or Loving
Light Pink = Happy or Cool
Purple = Joyful or Fascinated
Fortunately, the expressions of my favorite figures corresponded with my favorite colors, so I probably can live without attaining the full set. The full set is $72 after all. I should also mention that they couldn't resist that seemingly obligatory toyline gimmick of labeling this "First Series" -- so, if these do well, we can expect even more figures in the future.