how to mix colors by taking adjacent colors from the color being mixed?

[NotMephisto]

I want to implement a gradient overflow that takes primary color by picking up the closest colors from it and taking the invented color from primary, which invert does, however it makes it a dark color (although I think this can be fixed with set_lighness). There is no detailed information about this in the wiki. I would just like to make a nice shimmery button :c