When doing a Gram stain, Clostridium tetani stains purple— or gram positive— and it's a bacillus, meaning that it looks like a big cylinder or rod under the microscope.
Now, Leptospira is a tiny spiral bacteria, that stains poorly with Gram staining, because it doesn't retain the Gram dyes well, so it's classically considered gram-negative.
In the lab, when doing a gram stain, Clostridium perfringens is Gram-positive, or purple when Gram stained, and look like big cylinders or rods, also called bacilli.