What color wire is hooked to oil pressure sending unit on 1990 Chevy truck?

On a 1990 Chevy truck, the oil pressure sending unit wire is typically dark green/light green. However, it's crucial to verify this with your vehicle's wiring diagram. The color can vary slightly depending on the specific engine and options installed. A wiring diagram specific to your truck's year, make, model, and engine is the only definitive answer. You can often find these diagrams online through repair manuals or websites specializing in automotive information.