TAPPI T 527 om-19 specifies a procedure for measuring the color of paper or paperboard with tristimulus filter colorimeters or spectrophotometers incorporating diffuse/0 geometry and CIE (International Commission on Illumination) illuminant C.
Note 1: TAPPI T 524 "Color of Paper and Paperboard (45/0, C/2)" describes a similar procedure using directional illumination and normal viewing.