Background <p>This study evaluated the effects of CAD/CAM block type, composite resin type, restoration depth, and staining condition on the instrumental and visual color adjustment potential (CAP) of one-shade composite resins used for repair.</p> Methods <p>Three CAD/CAM blocks (Cerasmart, Tetric CAD, Brava Block) and four one-shade composite resins (Omnichroma, Vittra APS UNIQUE, Charisma Topaz ONE, ONEshade) were evaluated at two restoration depths (1 and 2&#xa0;mm). Color adjustment potential (CAP) was assessed using instrumental (CAP-I) and visual (CAP-V) methods under baseline and after staining conditions. Color differences (ΔE₀₀) were calculated using the CIEDE2000 formula. Data were analyzed using two- and three-way ANOVA, repeated-measures ANOVA and Pearson’s correlation coefficient (α = 0.05).</p> Results <p>All investigated factors significantly influenced CAP (<i>p</i> &lt; 0.001). Cerasmart and Tetric CAD consistently exhibited higher CAP compared with Brava Block (<i>p</i> &lt; 0.05). Restorations with a depth of 1&#xa0;mm demonstrated significantly greater CAP values than those with a depth of 2&#xa0;mm (<i>p</i> &lt; 0.05). Staining significantly increased ΔE₀₀ values and reduced both CAP-I and CAP-V (<i>p</i> &lt; 0.001). Instrumental assessments were more consistently affected by staining than visual evaluations. A significant positive correlation was observed between CAP-I and CAP-V (baseline: <i>r</i> = 0.591 &amp; after staining: <i>r</i> = 0.763, <i>p</i> &lt; 0.001), which became stronger following staining.</p> Conclusion <p>The color adjustment behavior of repairs performed with one-shade composite resins was influenced by CAD/CAM substrate type, composite resin type, restoration depth, and staining condition. Within the limitations of this in vitro study, staining reduced CAP, while 1&#xa0;mm restorations generally showed greater CAP than 2&#xa0;mm restorations.</p>