John in NM
Maple just a dark greenish grey. You can see the ends of a couple grey pieces at the bottom of the last pic. Those were the FA solution diluted 50-50 with vinegar and water. If I'd let the diluted solution stand for a few days the results would likely have been similar to the first and second samples, just not as dark. Pushing the solution more acidic causes the grey/green color, I think - ferrous acetate rather than ferric.

Baseline piece would just be regular maple, but I do know what you mean. I did this looking for a specific color, so I was more interested in comparing results than having a baseline for comparison.

Here's a pic of those other two pieces with the diluted solution:

The one on the left is diluted with water, then half of it washed with peroxide, the one on the right is diluted with vinegar and half washed with lye.