How easy is it to mistakenly grab a gun instead of a taser?

If you look closely at the body camera showing the moments leading up to the fatal shot that killed 20-year-old Daunte Wright, you'll notice the yellow handle of a Taser worn by the counterpart Kim Potter, the officer in question.
The bright color on a Taser is just one of a few key distinctions, meant to help prevent a mistake from happening.  
In fact, it's even laid out in the Brooklyn Center Police Department’s policy manual.
Section 304 mandates that "all TASER devices shall be clearly and distinctly marked to differentiate them from the duty weapon and any other device."

Tasers are also much lighter in weight and tend to have a different grip and feel when compared to a gun.
Also, if you're right-handed, your gun should be on your right side, says Maria Haberfeld, a professor at John Jay College of Criminal Justice who specializes in police training.
"You better have all the skills in the hand that is closer to the gun," Haberfeld says. 
She also says mistakes can occur, especially in a high-pressure environment.
"And when you are stressed, your peripheral vision is impaired, and this is what contributes to the confusion," Haberfeld says. "It’s rare, but it happens."
An accident is what Brooklyn Center's police chief--who resigned Tuesday-- called it Monday.
But Officer Potter was a 26-year veteran of the force.

And Daunte Wright's family attorney Benjamin Crump isn’t mincing words, saying his death was quote "no accident."
"After 26 years you would think that you know where and what side your gun is on and what side your Taser is on," Crump said Tuesday in Minnesota. 
"You know the weight of your gun, and you know the weight of your Taser. You know the gun is black, you know the gun is going to have some reflective color on it. So it is unacceptable."