How does one have all the non-empty sheets colored all at once

[Isko106]

I need a quick way to color all the non-empty sheets’ tab but have no idea how.

[Hrbrgr]

I did not quite understand your concern, sorry.

But there is an easy way to differentiate the sheets.
Click below on the tab you want to mark.
Select in the menu Tab Color.... Choose the desired color.