A very cool feature in Graph Builder:
After selecting some entries in the legend, the Color by Theme appears in the right click context menu.
So, if you want to give the items 1&2, 3&4, 5&6 ... the same color,
just select 1, 3, 5 ... and use Color by Theme - then repeat it for 2, 4, 6, ...
and you are done. Depending on the number of items, this can save you really a lot of time - compared to applying the color manually for each item.
Just one question puzzles me:
Why is Color by Theme not available for point plots?