Hi Keith,
I just finished a model about a month ago. I used matte board (picture framing material). It comes in 100's of different colors and the surface color is fairly thin so it can easily be engraved off to reveal the core color. Usually either black or white which comes in useful for engraving details such as shutters or shingles or different types of sidings. It also comes in large sheet sizes.
The attached pic doesn't show a lot of the engraving detail but the matte board does work really well.
Later,
Ken