The smoke color isn't clear, ... This Boston Globe video shows a grayer color for the bomb in the foreground, and a darker color for the second bomb in the background.

The color of that smoke depends on what those particles are made of," Robert Krampf, a science educator who calls himself the Happy Scientist, told CBS News via email.

For white smoke, the Vatican says it used to use wet straw, but to make it a more pure color, instead of a confusing grey, they use potassium chlorate, lactose and a tree or bush resin called ...

The color of that smoke depends on what those particles are made of," Robert Krampf, a science educator who calls himself the Happy Scientist, told CBS News via e-mail.

Now, they use a mixture of potassium perchlorate, anthracene and sulfur to color the smoke, according to the Vatican. Historically, the election ballots are burned with this mixture, ...