Color Variability of European Oak Veneer Packages: An Exploratory Colorimetric, Chemical, and X-Ray Diffraction Study

European oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) is widely used for decorative veneers, but natural color heterogeneity complicates package matching and industrial sorting. This exploratory study characterized one processed veneer package from each of eight commercial provenance labels: Szczecin, Krotoszyn, Zielona Góra, Wrocław, Katowice, Krosno, and Lublin (Poland), and Wittenberg (Germany). Each package was assessed visually and by ten CIELAB measurement points, while package-level subsamples were analyzed for ethanol-soluble extractives, cellulose, lignin, and X-ray diffraction characteristics. Package means differed most strongly in lightness (L* = 59.4-69.7); however, within-package L* ranges reached 10.7 units and overlapped the differences among package means, showing that package means alone are insufficient to demonstrate provenance-based sorting. Exploratory correlations based on eight packages indicated that higher extractive content was associated with lower lightness (Pearson r = -0.80, p = 0.017; Spearman ρ = -0.75, p = 0.033), and the association remained negative in all leave-one-package-out recalculations (r = -0.96 to -0.72). In contrast, apparent Pearson lignin/color associations were weak in rank analysis and changed sign after exclusion of P5. Associations of the Segal crystallinity index with color were directional but not statistically conclusive at n = 8. All diffractograms showed cellulose I reflections near 15-17° and 22-23° 2θ; approximate CrI values ranged from 48.0% to 66.2%. The results support combined colorimetric and chemical characterization for package-level quality control, but independent replication across multiple packages per region is required before any geographic origin classifier can be validated.