Ok, on the surface this might sound like a dumb problem but hear me out. I currently have my pen toggle switches set to "previous tool" and "color picker" (Ctrl key). I love these settings for painting. However, when I'm sketching using black and my finger invariably slips down and hits the lower "color picker" toggle then I end up with the white background as the new drawing color (which of course is useless) and then I have to reset my color to black to start drawing again.

Now I know I can change the settings of the pen when I know I'm going to be sketching but I don't want to . What I would prefer would be to hit a hotkey to disable the color from changing until I want to enable to it again. It would save time but more importantly, at least for me, frustration at having to reset the foreground color.

Any have a better solution I'm overlooking? Any chance anyone else would like to see a similar tweak in their workflow?

You're holding it wrong (I do a similar thing but my lower stylus button is Space/Pan so it's not as serious an effect, but still annoying.)

If you're doing long concentrated lineart sessions, you could use white paint with your active layer set to Subtract blending mode over a white background, then you'd get black paint strokes and it wouldn't matter if you accidentally colour picked the background colour. There is a chance that you'd sometimes pick up black and then paint 'nothing' but that should be rare with lineart. A final Merge down would give you a working end result.

Unless you can retrain your fingers, this is all I can think of.