If you want to get a correct color match for the Lionel Daylight engine, I'd suggest getting Lionel passenger cars. Other manufactors' cars may not have the right colors to match your engine. The two sets below are the best ways to go. Just my opinion. Both the Madison cars and the streamlined aluminum sets are very nice. If you can find  Williams streamlined aluminum passenger cars, those would be fine, too, as they are similar to the Lionel aluminum streamlined cars and a good match for the engine. You may have to purchase some of these cars individually, but sometimes you'll find them as sets. Both sets were made quite a few years ago, so you'll have to find them in the secondary market, such as Ebay. Also, with respect to the streamlined aluminum cars, there were 8 different ones made; only five of them are shown below, plus the single vista dome car shown. The larger picture shows the vista dome car, which was an additional car to the 5-car set.

Lionel 6-19019, 6-19023, 6-19024, 6-19025, 6-19026 Southern Pacific Daylight 5-Car Madison Passenger Set

Five painted aluminum Southern Pacific O guage passenger cars including baggage car #6-9589, combo car #6-9590, passenger car #6-9591, passenger car #6-9592, observation car #6-9593