My own version of ivy's Darker RetroDays Sidewalk edition, that recolors the rest of the tiles to match the dark viridian, and made a matching base_colors to match. Some tiles from Retrodays+ were also used. I only tested it in Bright Nights, but it should be fine in other forks.

Paste the entire RetroNights folder into CDDA's gfx folder. go to options > graphics > tileset > RetroNights

Paste the base_colors.json and put it in your config folder. If you don't have one, make one in the main CDDA folder. Note that this will overwrite the original base colors, so back up the original one.