Thanks for the answer. Yes, exactly—the ability to color the map using 'per map cell.' The charset, screen RAM, and color RAM aren't tied together in any way, so I can use a single character anywhere on the screen and assign it any color at its position in the color RAM. 0-7 for hires; 8-15 for multicolor. I don't see any reason why this should be RAM-intensive; the RAM itself never changes. One character, one color (11).
Yes, I considered using 1x1 tiles, but then a problem arises: I’d have to—pointlessly, in my opinion—duplicate characters in the tileset just for the sake of the color on the map. Technically, I really don't see an issue why map coloring couldn't be free and not tied to a specific character or tile. Any character on the map should be able to have any color (0-15). Or am I wrong? :) Besides, if I use a 1x1 tileset, it’s basically just another redundant table for the map and extra code for map rendering, all just because I can't directly define the color at a specific map location without defining a character or tile first. The option to change the color (11) for a cell on the map as needed shouldn't have any impact on memory usage. It’s just changing a value at the exact same location in the map data. However, I don't know how you have it technically implemented in the software.
On the left is the current state. Each block requires a separate character just for the sake of the color. On the right, it would be enough to have the option to color the selected map cell from the palette. It’s nothing more than changing a value from 0-15 in memory, where some value must already exist anyway.
A 1x1 tileset, or any other format for that matter. On the right is the current state. Yes, a single character is used if compression is involved, but the tileset still generates redundant copies of the same character just to handle different colors. On the right, it would be enough to simply color a selected cell from the palette. Basically, the same rules apply as without a tileset, since color (11) can be any value from 0-15 in every cell on the map. I don't believe that locking the color (11) to a character or a tile is necessary.
The C64 has no 'one color per character' restriction ;) Of course, that's assuming we aren't talking about standard text mode.