Allow manual override for mapColor

[overdramaticpanromantic]

Describe the content or mechanics you are proposing.

Currently, the game sets the map color after parsing the file. I propose that the mapColor variable for environmental tiles be made to where it can be overwritten in the tile's file.

Describe how you think this content will improve the game. If you're proposing new content, mention how it may add more gameplay options or how it will fill a new niche.

Depending on how the environmental tile's sprite is made, the game can choose the color to use very differently. If, say, the wall and the floor of a biome use the same palette, then the same color might be chosen, making the biome very hard to discern on the minimap. An example is posted below, wherein the floors should be darker than the walls, but aren't.

Before making this issue, check the boxes below to confirm that you have acknowledged them.

• [X] I have checked the Trello to make sure my suggestion isn't planned or implemented in a development version.
• [X] I am familiar with all the content already in the game or have glanced at the wiki to make sure my suggestion doesn't exist in the game yet.
• [X] I have read README.md to make sure my idea is not listed under the "A few things you shouldn't suggest" category.

[overdramaticpanromantic]

As it turns out, it's defined by the center four pixels, which can usually be accommodated for.