## 4 Discussion
This observation may support the presence of blue and emerald-green luminosity captured in the following frames, as shown in Figure 2.  
The movement of the cloud towards the camera location supports the hypothesis that the IC flashes occurring within the dense cloud can be observed as colored luminosity. However, the depth of the clouds obscured the flashes, leading to unsuccessful GLM detection. This suggests that the clouds are particularly dense, with cloud particles potentially dispersing light from the lightning flashes. As illustrated in Figure 5, the group energy plot exhibits a pulse-like behavior rather than a gradual increase. This characteristic aligns with the study that there is no gradual rising pattern in the group energy of CG flashes, whereas such a pattern exists in IC flashes [49]. Assuming this pattern, CG may have occurred during the period marked by the green and light blue dots, indicating a potential occurrence of negative CG discharges during that time. Since strokes, particularly the first return strokes, in CGs tend to exhibit strong luminosity at the cloud-top, the GLM has a tendency to detect illumination from other processes in CGs, resulting in higher detection efficiency compared to IC [49]. Additionally, Ref. [49] reported that longer channel lengths and flash durations increase GLM detection efficiency. However, Ref. [50] noted that flashes occurring within storms, which often have short durations, may not always be detected by the GLM. Therefore, it is possible that there were flashes during the observation period that the GLM could not detect. In Event 2, the trajectory of all the dots from red to violet is almost along a straight line and is located near the edge of the cloud area, as illustrated in Figure 8. These dots are replotted in Figure 13, representing the zoomed-in view of Figure 8, with coordinates of 26.15\({}^{\circ}\) N-26.16\({}^{\circ}\) N and 81.68\({}^{\circ}\) W-81.76\({}^{\circ}\) W. The dots within the blue box and the pink box are magnified, respectively. The cluster of orange dots is displayed in the bottom right of the map. The last eight orange dots, ordered from 10 to 17, are closely situated, suggesting that they propagate upward with angle, and the propagation may be branch-like. The location of the yellow, green, and light blue dots indicates that the discharge location is not continuous, which may support the fact that the propagation is not branch-like. Therefore, the event may have exhibited different discharge behaviors during the event time. As shown in Figure 9, higher group energy is detected during the time window corresponding to these different behaviors. This observation supports the hypothesis that discharges with different behaviors exhibit different types of light emission. Assuming a branch-like discharge, there may be more collisions with nitrogen molecules (N\({}_{2}\)) or nitrogen ions (N\({}_{2}\)\({}^{+}\)), resulting in the emission of pinkish or violet light. Conversely, non-branch-like discharges may involve collisions with oxygen atoms (O), emitting blue to emerald-green light. For this event, the discharge path occurred in a time duration of 2.0 s in the same location. The atmospheric condition is considered almost constant within this short timeframe. If so, the change in color of the luminosity could be attributed to the location of the discharge path, with the light dispersed with the interaction between the discharge and unique cloud particles. These interactions may be associated with characteristics of the discharge, such as the temperature of the leader with positive or negative polarity or the composition of molecules at different heights and horizontal distances in the air surrounding the area. During the timeframe of the light blue dots, dots numbered 1 and 2 were located closer to the camera than the other dots. Light blue dot number 2 occurred at 10.228 s, and its energy was the highest during the event, corresponding to the frame of emerald green.