I just recently got back into designing and coding from a long time ago. The idea was to use the RGB values, such as “Red” to determine terrain type, and Green and Blue to help determine some elevation and weather characteristics, etc. The weather would be more or less derived by location (distance from poles) and terrain type.
I never actually painted the map, but I included some live MUD screenshots (I had to debug it a bit lol).
From a terrain point of view, it’s easy to convert real-life colors, such as white for polar ice, green for forest, different green shade for fields, brown for mountains, etc etc, and convert them into a readable bitmap for the game code (where R=1 means one thing, R=2 means another, R=3 etc etc - screenshot of code shown) – since looking at the map itself would be mostly “black” as far as terrain.
I chose a bitmap because according to my load time logs, the wilderness loading took almost zero time at all.