While I haven't been reloading for 40 years I've done something similar.
Since I use the Lee Dippers I pour some the powder from the bottles into glass containers making it easier to scoop. Well I was loading up some light 44 mags using Bulls Eye. The jar was getting low, so I decided to fill it back up. Grab a bottle, poured it in and continue on my way. After charging 5 shells I notice little red flakes floating around in the powder. I stood there thinking, I don't remember little red dots in my powder. Then it hit me, I had poured Red Dot into my Bulls Eye jar and was charging my 44 mag cases with some bulls eye/red dot hybrid. While they burn around the same, and the charge was under what would be considered max for either powder, I wasn't about to find out how a hybrid powder like that would shoot...
There was hardly any Bulls Eye left in the jar when I poured the Red Dot into it, but I wasn't going to take any chances, especially with quick powders like that. Went outside and poured it into the plants.
That's what I get for not checking the bottle when I was pouring it. I had no distractions going, but my attention was wondering, I was thinking about what I was going to load next. Luckily I caught it before anything bad could have happened. But even without distractions, reloading requires your full attention.