The urban canopy refers to the spatial area at the average height range of urban structures. The light environment of the urban canopy not only influences the ecological conditions of the canopy layer region but also serves as an indicator of the upward light influx of artificial nighttime light in the urban environment. Previous research on urban nighttime light environment mainly focused on the urban surface layer and urban night sky layer, lacking attention to the urban canopy layer. This study observes the urban canopy layer with the flight and photography functions of an unmanned aerial vehicle (UAV) and combines color band remote sensing data with ground measurement data to explore the relationship between the three levels of the urban nighttime light environment. Furthermore, a three–dimensional observation method is established for urban nighttime light environments based on a combination of three observation methods. The research results indicate that there is a good correlation between drone aerial photography data and remote sensing data (R² = 0.717), as well as between ground–measured data and remote sensing data (R² = 0.876). It also shows that UAV images can serve as a new path for the observation of urban canopy nighttime light environments because of the accuracy and reliability of UAV aerial data. Meanwhile, the combination of UAV photography, ground measurement, and remote sensing data provides a new method for the monitoring and control of urban nighttime light pollution.

Historic-district maintenance and repainting may preserve familiar colors while altering relationships among roofs, facades, and architectural accents. Conventional palette surveys identify which colors occur but provide limited information about their component assignment and relational structure. This study develops a component-relational framework integrating architectural assignment, directional color differences, and recurring building-level configurations. The framework was applied to 153 selected historic buildings in Dalian, China; 149 complete roof–facade–accent cases were analyzed using normalized image-derived descriptors in CIELAB/CIELCh, CIEDE2000 color differences, repeated-measures tests, and exploratory clustering. The components occupied a shared warm-to-neutral gamut. Facades were generally lighter, whereas chroma showed no consistent ordering. Within the standardized dataset, roof–facade separation was lower than both roof–accent and facade–accent separation, while similar overall magnitudes arose from different combinations of lightness, chroma, and hue. Five overlapping configurations represented recurring relational centers rather than discrete styles. This study contributes a transferable component-relational method that extends palette inventories into comparative accounts of architectural color structure, supporting more precise analysis of historic-district color conservation.

Present-day colours of historic buildings reflect inherited fabric and subsequent interventions. We analysed Roof, Facade, and Accent colours in 153 surviving buildings in Dalian, China, across four construction periods using CIELAB lightness (L*), CIELCh chroma (C*), Hue Family, district-adjusted models, and spatial statistics. Significant period associations occurred for Roof lightness (partial R² = 0.125, q = 0.003), Roof chroma (0.107, q = 0.005), and Facade chroma (0.115, q = 0.003), remaining significant after grouped-function adjustment. Roof Hue Family also differed by period (Cramér’s V = 0.359, q = 0.007). At k = 4, positive global spatial dependence occurred for Roof lightness (Moran’s I = 0.188, q = 0.030) and Facade chroma (I = 0.158, q = 0.011), but not Roof chroma. Two local Facade-chroma configurations were identified. Neither global association remained significant after period and district adjustment (both q = 0.939). The findings distinguish construction-period differentiation from spatial continuity and support component-level colour documentation, comparative conservation assessment, and future monitoring.