Task: I am going to change my phone but before that I wanted to remove all my Gmail data from my phone , Sign out of the Gmail app 
Steps:
Open the Gmail app
Click on the C Profile icon at the top right side of the screen
Click on the Manage accounts on this device option
Select the Cole2dbwpersonatest2@gmail.com account
Click on the Remove account button
Click on the Remove account button in the pop up