Roman Column at the Forum

In Rome, Italy at he forum

Roman ruins conjure past glories and defeats once mighty empire now reduced to rubble with a crown of red roses

That anything remains at all from such a long time ago is a marvel. The columns one the white classic looking column and the other a brick column. Why a brick column? Is it a repair? A repair from what era? When was the repair made? Possibly a time that would be considered ancient except for the fact that it is surrounded by older ruins?