Yes — X-Rite publishes reference colorimetric data for the ColorChecker charts. On the product page, look under the Specifications tab for a link such as “Colorimetric data (PDF).” The published data includes CIELAB values for ColorChecker Classic and ColorChecker SG charts.

Important: X-Rite changed the formulation around November 2014, so you need the data that matches your chart version (before or after November 2014). Using the wrong reference set can give inaccurate results.

Also note that the patches are not perfectly permanent: long sun exposure and age can shift them, and X-Rite recommends replacing charts periodically (commonly about every two years). So even with official data, an old or heavily used chart may no longer match the reference closely.

In short: the values are public, available from X-Rite’s downloadable colorimetric PDF, and you should use the correct pre-/post-November 2014 dataset for your specific chart.