Because even the most seasoned bunker dwellers need a refresher on the basics of light.
Here are the basics: Black, White, and Grey (and sometimes, just Grey). The Brightness Spectrum is the foundation of any good bunker aesthetic.
Black is not just black. No, no, no. Black is a mood, a feeling, a way of life. It's the absence of light, the end of hope, the start of despair. Black is...
Actually, black is just a really dark grey.
White is not just white. No, no, no. White is a beacon of hope, a shining star in the darkness of the bunker, a signal fire in the night.
White is...
Grey is the compromise between black and white, the bunker equivalent of 'I'm not really sure'.
Grey is... well, grey.