just answering to file transfer problem: i'm using https://filebrowser.org/ for my clients to upload images and videos. it doesnt have solutions for choppy internet tho.

for that, i could recommend https://syncthing.net/ that synchronizes folder contents, and can resume if there's network problems. however you'd need to create a process that moves the synchronized files out of the folders once done, to prevent buildup at the client side. i would recommend using a separate share for every reporter...

Exactly like the image taken by your cell phone is actually black and white, and the colors are only added when you view the image with a special software. Namely, every photosensitive sensor is exactly the same, and they only measure brightness, without color. However, the light gets filtered with red, green and blue filters before the light hits the sensor, so that different sensors get different color of light. But still the analogy stands. With telescopes you might filter the colors differently, or even acquire the different 'colors' at different times or locations, but the principle is the same as in your cell phone.

cheers.