56 Caddy brochure shows blue engine with red valve covers (stock)
http://www.oldcarbrochures.com/static/NA/Cadillac/1956_Cadillac/1956_Cadillac_Brochure/1956%20Cadillac-02.html
here's an idea for the kit...
http://public.fotki.com/Rikster/11_car_photos/beautiful_custom_cars/valley_customs-1/jack_stewarts_polyn-3/jack_stewarts_polyn-2/