Blueberries (Vaccinium spp.) exhibit a high degree of asynchrony during flowering, fruit set, and ripening. Fruit pigmentation is highly dependent on direct solar radiation, resulting in significant differences between sun-exposed and shaded berries within the same cluster. This study evaluated the effect of two plant growth regulators (PGRs), abscisic acid (ABA) and methyl jasmonate (MeJas), on fruit coloration and firmness under in vitro conditions. Clusters from two cultivars, ‘Duke’ and ‘Brigitta’, were collected at the green berry stage, two weeks before the expected start of commercial harvest in the 2024–25 season. Half of the clusters were taken from the outer canopy (sun-exposed) and half from the inner canopy (shaded). In the laboratory, clusters were placed in Falcon tubes with their twigs immersed in one of six solutions: (1) water (Control 1), (2) sucrose (Control 2), (3) ABA 500 ppm sucrose, (4) ABA 1000 ppm sucrose, (5) MeJas 0.1 mM sucrose, and (6) MeJas 1 mM sucrose. The samples were maintained in a growth chamber under controlled temperature (22 °C) and photoperiod (16 h light at 70 µmol/m²/sec). Fruit were evaluated at 3, 6, and 9 days post-treatment for coloration (percentage of blue fruit) and firmness (g mm⁻¹). ABA treatments significantly accelerated fruit coloration in both cultivars. In ‘Duke’, ABA-500 and ABA-1000 reached 80% and 100% blue fruit by day 6, respectively, compared to
