A method of converting reflectance spectra to a convenient intermediate form introduced as LabPQR is used as an Interim Connection Space (ICS) within a spectral color management system. The LabPQR ICS makes use of a spectral encoding that explicitly incorporates colorimetry with additional dimensions that define spectral error corrections that allow an inverse transformation to approximate the original spectra. Consistent with a previously defined spectral color management transformation chain, the PQR dimensions of the ICS can be optimally formulated to suit any specific output device's spectral characteristics. Several example transformations are demonstrated using various output devices with spectral gamut visualizations. Observations are made, and from these observations, a possible method of performing spectral gamut mapping is proposed.