Follow the steps below to be able to change the look of your table borders made in Google Docs using an iPad:
Step 1: Select the cells
Good Docs needs to know which borders you want to change, so select those borders first.
Step 2: Change the border settings such as border color, width, and style
Alternatively, you can also access the table border settings by clicking the Border Icon as seen below. The Border icon will only be shown if you select the cells first.