Class: https://github.com/Railcraft/Railcraft/blob/liach-1.12.2/src/main/java/mods/railcraft/common/plugins/color/ColorPlugin.java#L26

Any Item or Block Class that calls:

ColorPlugin.instance.register(this, this);

will fail because "instance" is null. Verified with debug.

Confirmed in Production mode with Railcraft ONLY, no other mods.

Stumbled upon fix, pushing PR shortly.

Fixed in #1416. Thanks doc! btw the blast furnace is fixed in the last commit.