Why do Noctilucent/Cirrus Clouds turn dark blue/black?

Today there was a thunderstorm where I lived in the day, I saw weird blue clouds weigh above the sky and a whole bunch of cirrus, all of a sudden both turn dark blue for a while and rain and pour, there is also orange/purple lightning, all of a sudden it stops and there is a heavy drought, it get really hot, at 4:00 I see the cirrus clouds turning black and noctilucent clouds (weird clouds) turning the darkest blue can go, then all of a sudden the sky turns black. My dad is meteorologist and he told me cirrus and noctilucent clouds turn black, I asked him why clouds turned black and he replied with "All clouds turn black not just a specific set of clouds all clouds turn black because they are blocking the suns light out and all forms of light, even at night there is no sun but the clouds block out light, it's not just sunlight they block out." I replied with "I think I understand." I then left. There is a severe storm where I live, it's down pouring and there is red/purple lightning and not only that it's dark out in the city in the part I live in.