I think the toxicities of colonial/postcolonialism can be drawn out more in how they relate to the message you are trying to convey through the use of this image. Perhaps also elaborate more on what PM2.5 is and its effects.
The caption can be elaborated to include more specific information about how the author is tying colonialism to a discussion of PM 2.5, as this seems to be an important part of why they chose this image. More clarity can also be offered around the positionality of NGOs such as the Lung Care Foundation, and the impact campaigns such as this may or may not have on forms of environmental justice activism, especially in terms of how it may impact particular groups rather than others.
I am also curious to hear more about the actual Diwali celebrations and the forms which fireworks take- where are they set off, how many, what is the resultant impact for PM levels compared to “typical” levels in Delhi, which are also very high?