The census enumerators books were regarded by the GRO as the raw material from which to produce the tables published in the 'Census Reports'. In this process the books were altered and annotated, on the original books these are in coloured inks, crayon, or pencil, and can easily be differentiated from the enumerators' returns. On monochrome microfilm these additions are difficult to differentiate. For examples of actual census pages in original colour see http://tinyurl.com/2wpx2g which is RG13 piece 297 folio 22 page 1, and http://tinyurl.com/233wwl which is RG13 piece 1835 folio 94 page 35. Stan