Benjamin and Christina Blue Marshall are buried in the Fraserview Cemetery in New Westminster. I have Marshall family buried there also (James Marshall and Isobella McNicoll Marshall) and am familiar with where Marshall plots are at that cemetery.
The monument is in the north part of the cemetery, rather tall, with a carving of an urn draped with a cloth on top. I see it each time I drive by.
Sorry I can't be more precise, but would be glad to show it to anyone who wants to see where it is.