Wash the berries and throw them in the blender with the water still clinging to them. Whiz them until they are totally pureed. I strain them because I don't like a ton of pulp in my fruit pops but if you like the pulp (i HATE seeds in my fruit pops too, in case you were curious), don't bother straining. On the other hand if you hate ANY pulp, you can strain them more than once.
Put the blueberry juice back in the blender with the vanilla yogurt and the buttermilk and whiz until completely blended.
Pour about 1 or 1.5" of this mixture into each mold. Put the mold in the freezer for at least 45 minutes to set up. Now pour about 1/2" of the blueberry pom juice in each mold and return to the freezer for 45 minutes. Take out and add another 1 or 1.5" of the blueberry/yogurt mixture. Lather, rinse, repeat until your molds are full and let them sit for at least 4 hours but if you can let them either sit all day or overnight, it's even better.