The color varies widely based on multiple factors:
- Lighting
- Paper type (I'll get there in a minute)
- Scanner type and quality
Therefore, I can't 100% give you a color estimate (it could be anything from very light yellowish-gray to very dark gray).
As for paper types. There are also several types of paper that could be used for printing manga:
- Newspaper-like paper, which is thin and has a slight gray shade.
- Recycled paper, which is yellowish in composure and often has little "grains" in it.
There are probably a whole lot more, but that's the prominent two I know of.
