system
Given the following post, respond as if you're commenting on Reddit:
human
Why are blueprints always that colour?
gpt
They're not really anymore. They were for a long time because of the method used to make them. Special paper was treated with chemicals that would be hit with light passed through something like an old slide projector. The lighted image allowed for the white lines to show up. Now, we have big printers that are just like the one you might have on your desk, so you can just print big diagrams with color and everything.