Subways are central to underground transit environments and subtly influence passengers’ moods and mental states, yet the effects of lighting and decorative design remain underexplored. This study employed a within-subject design in which 21 participants experienced nine virtual subway environments, generated by crossing three illuminance levels (300, 500, 750 lx) with three lighting–color ambience configurations (2700 K–green, 4300 K–blue, 6500 K–white). Functional near-infrared spectroscopy (fNIRS) was used to measure prefrontal oxygenated hemoglobin during stress-inducing tasks, alongside PAD mood ratings, the Perceived Restorativeness Scale (PRS), and the State-Trait Anxiety Inventory (STAI). Results showed that the 500 lx, 4300 K blue–sky environment produced comfort and restorative effects, which were accompanied by increased DLPFC–AFC functional connectivity. Higher illuminance (750 lx) was associated with increased subjective alertness and greater prefrontal activation, alongside reduced perceived restoration. This pattern was associated with greater neurocognitive engagement under higher illuminance conditions, although the underlying neural mechanisms require further investigation. In contrast, the 300 lx, 2700 K green-toned condition was associated with lower restorative ratings, indicating context-dependent differences in affective responses across lighting configurations. Overall, the findings provide evidence of condition-dependent relationships between illuminance, color ambience, and both subjective and neural responses within a controlled virtual subway context.