Answer
what shape do most colonial style squares have in latin america?

Rectangular shape

Explanation:

The cities built by Spanish colonizers followed Royal ordinance, which stipulated the shape and extension of the Main Square, the width and direction of public roads, and the distribution of blocks, following a grid plan, in which streets run at right angles, so blocks have a square or rectangular shape. The Main Square or Plaza Mayor remained the center of community life, usually at the center of the city, and held usually 3 related institutions: The cathedral, the administrative center, and the law court. It was an open space in rectangular shape.