ANSI is a graphics standard in DOS which allowed a certain set of escape sequences to be included in files that would produce color. Towards the early 1990's, an entire ANSI "Scene" rose up where people tried to outdo each other producing elaborate ANSI images and files.

As an example I've included a selection of very fine ANSi art from ROY/SAC.

ANSI on this page are rendered with a nice JS library called escapes.