Well if in doubt, do not change configuration while on the touch n go. There, problem solved. Keeps you safe.
If you can't safely complete the following touch n go without the absolute requirement for a configuration change in haste (the presumption is that you're so task saturated with the task of configuration change while in the touch n go, that switch misidentification is highly probable in your mind), then you got bigger problems in the task management, SA, and planning areas of airmanship.
I go back to all the piston complex aircraft I've flown and though I never had a problem making configuration changes on touch n go ground roll, I never NEEDED said configuration change to effect the touch n go to obstacle clearance as required by present conditions. Which is to say I didn't need to effect a configuration change, I only did so for bonus points. So if you're that concerned about your task saturation, don't touch it, just go.
Stay safe!
As to looking inside or out, good God brother, look INSIDE without sacrificing aircraft control (combination of peripheral vision to maintain track and minimum time required focusing on the switch, accomplishes this) and confirm the damn switch. If you can't accomplish this, just go without the change!
What's the point of keeping your eyes safely outside when you flip the wrong switch and suck up the gear now.