Where to find the paint palette
ScreenHype places the customization area at map coordinates 3570, 1190. From the early area, look across the river for a scaffolded structure with green, yellow and red walls and a large paint palette on the green wall.
The same guide recommends turning on the nearby lantern or wall light because the space becomes hard to read at night. If your group does not have the map yet, return after earning the Red Tower key and opening the Map Room.
How painting works
You cannot paint yourself. Another player picks up the paintbrush, taps a color on the palette and aims at your head, upper body or lower body. The game shows a target circle over the part being painted.
Each of the three body sections takes one palette color at a time. There is a mirror on the right side of the area, so the person being painted can check the result and ask for changes.
What persists
ScreenHype reports that chosen colors remain after reloading a run. Until this wiki verifies that directly, treat it as a community-tested note and keep a before/after screenshot if your group is documenting the feature.
Because the mechanic needs a second player, the customization space is a good first place to teach new players that Big Walk often turns simple actions into co-op rituals.