Color Code People By Generation

You want to color all of John Doe's gg grandparents, grandparents are the third generation so gg grandparents must be the fifth generation of ancestors.

Tools - Color code people -- choose a color and choose "People selected from list."

find "Doe, John" 
Click Mark group, ancestors - 5 generations -- OK
Click Unmark group, - ancestors - 4 generations -- OK
OK

If you want the 4th generation a different color, just color 5 generations one color, 4 generations another color, 3 generations a third color, 2 generations a fourth color and the starting person a fifth color. 
With enough colors and enough patience you can color every generation a different color.

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You can do descendants that way too.