Late model 240s tend to have dark grey rocker panels. There have been questions in the past about the paint code, and I couldn't find any precise information.

However, today by accident I found that my brush-on Por 15 High Temp "Manifold Gray" model 44216 is a pretty good match. It depends upon the fading of your own rockers, but it looks nice. The best route would be to have a shop make you a can of matched paint. I just painted my rockers (and my new header) with the "Manifold Gray". Although, I do not know if it will cure properly because it will not reach high temperatures on the rocker panels. I will find out in time. (If you use this specific paint it must be done in a well ventilated area and a quality respirator must be used.) I caught one of the last warm days here in Iowa to do it outside with a good respirator. It is an extremely pungent paint.

The same color is apparently made in a spray can, too (model 44218), but I haven't used it.