I have multiple polygons aligned next to each other. They are colorfilled with "Graduated" style. I have changed "Stroke style" to "No Pen". How can I get the hairline between the polygons to disappear, so it is only the color fill one see?
The easiest way is to have a small border and set that border to the same color as the polygons.
This can be done automatically by setting the border color to @symbol_color.
So graduated symbology, click on the Symbol at the top without highlighting any of the individual classes, this means that all of them will be edited:
Then we set a data defined override for the stroke color:
Which is just set to @symbol_color, which will use the same color as the main color: