Since Vectorstyler version 1.3.012
Creating a color palette from a selection of shapes
now also takes duplicate colors into account. You have
to deselect an option in the color palette Menu for that.

Here the Steps:

Open a color palette
Menu > Window > Color Palette

In the color palette, go to
Menu > Options > uncheck " Collect Unique Colors "

Select your objects, which may contain duplicate colors now
and choose "Create Color" > "Create Colors from Selection"

This feature is very helpful for all kind of color pattern and creating gradients.

Here the related Tutorial for creating multicolor gradients:
https://www.vectorstyler.com/forum/topic/5694/way-to-create-a-multi-color-gradient-from-colors-of-a-color-palette

Here a pic