I was down in the DC Friday night during the thunderstorm outbreak a/k/a derecho. One of the extraordinary things was that as the storm rolled in at 10 p.m. or so, the clouds looked red when the lightening lit them up. Don’t know why that would be, but here’s a video that captured it.
From commenter Ben S:
Most atmospheric coloring, from blue skies to the yellow sun (in space it looks white) to red sunsets are due to Rayleigh scattering. You get different colors depending on which wavelengths of light are scattered, how much they’re scattered, and how all the scattered colors then mix together.
In this case, the light from the lightning is traveling through a lot of air and water vapor so it’s scattering a lot like a sunset, and while that same red glare is going to be happening when lightning strikes during the day, you only see it at night when there’s little ambient light; same reason you can’t see stars during the day.