I have an 87 buick century limited with light grey exterior and a darker gray interior. How can I determine the exact color of the headliner material?

The best way to match any kind of material is to send a sample to us so we can compare to the actual headliner material rolls, but it's a good bet the color is smoke (medium gray) or charcoal (dark gray), GM used both these in the 80's.

A small to mid sized car headliner kit will work for the 87 Buick Century.