Coloring defaults for images I do include lowbrightness set to -0.24 instead of 0.24. The apophysis default was -0.24 so I use that. Gamma Threshold 0.2. I raise the contrast to 1.25 and to make up for it, I raise the saturation to 1.07. If it’s still too bright I raise the Fade to White value above 250 but rarely go over 300. Image brightness and gamma depend on the variations used. 4.0 gamma usually but if I want more detail to show up lower values and more but flatter color higher values. That’s where I start and adjust further as needed from there.
When I’m doing black and white “coloring book style”, I increase the anti-aliasing amount to .5, and decrease the radius to.05. This makes thin, crisp lines. Then I use the Erode operator in post processing to make the lines thicker. For most fractals though, all I do is increase the brightness.