To tint a piece of furniture, hover over it with the mouse, then press (and hold) one of the hotkeys to increase the red, green, or blue tint of an object.
Default hotkeys are:
Red: NumPad 1
Green: Num Pad 7
Blue: Num Pad 9
Reset tint: Num Pad 3
If you hold down a mod key (default Left Alt), it decreases the respective tint instead.
Furniture recolor is tied to the furniture's placement, so moving or removing furniture pieces resets their tint.
You can edit all the config variables using Generic Mod Config Menu, or editing the config.json file.
See also Furniture Adjustment for shifting placement of individual furniture pieces.
Technical
Requires SDV 1.5.5+
Requires SMAPI, uses Harmony.
Compatible with Mod Updater for automatic updates.
Code is at https://github.com/aedenthorn/StardewValleyMods.
If you want to complain or ask for help or help me test my mods, you can visit my Discord server.
A list of all my mods for Stardew Valley is available at https://www.nexusmods.com/stardewvalley/articles/895.