Inspired by Highlighted Jars, this mods colors empty machines so they're easier to spot. Works for every vanilla machine and also Producer Framework Mod machines. Additionally, dims "invalid" machines (machines in locations they don't currently work - ie casks in locations that are not valid for them, or PFM machines with location/weather/season restrictions.).

Install

Install the latest version of SMAPI.
Download and install AtraCore.
Download this mod and unzip it into Stardew Valley/Mods.
Run the game using SMAPI.

Uninstall
Simply delete from your Mods directory.

Configuration
Run SMAPI at least once with this mod installed to generate the config.json, or use Generic Mod Config Menu to configure.

The coloration (both the EmptyColor and InvalidColor) can be set independently. If you have GMCM Options installed, these will be color selectors. Otherwise, it'll be a text field where you can enter any color name from Microsoft's long list here, an HTML color code starting with # (ie #FF0000 for red), or list of numbers (ie 255, 0, 0 for red.)
Every machine (including PFM machines) can be configured independently. If you have PFM machines, please load into a save before configuring - the PFM machines are not loaded until the save is.

Mods in screenshot
The mod machines in the screenshot are from the excellent Artisanal Soda Makers by Hadi!

Compatibility

Works with Stardew Valley 1.5.6 on Linux/macOS/Windows.
Works in single player, multiplayer, and split-screen mode. Should be fine if installed for only one player in multiplayer.
Should be compatible with most other mods. Tested with Producer Framework Mod. Currently does not affect DGA machines; I'll add that in later.

Highlight Empty Machines

AtraCore