How to save the acquired 2D point cloud in map_server with a color other than black and white

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I want to draw a 2D point cloud with acquired position coordinates in a color other than black and white in ros's map_server png file. I am open to any method, but would prefer to use ros in python code if possible.

2D point clouds acquired using occupancyMap were stored in a list and plotted on the image using opencv. However, there is a problem that the point cloud is updated in the list due to the occupancyMap code, and the scale of the map does not match.