Okay then don't use it. The entire point of KDE is to provide a traditional desktop metaphor that windows users find friendly.
And if you're especially irked, KDE like most FOSS is somewhat community driven, so be the change you desire if that's your kind of thing. Or don't do anything but complain. You're completely free to do whatever.
But that said, you may perhaps be making a mountain out of a molehill, especially UI elements that if MS wanted to cite copyright, they would have done it long time ago. This has been the default color picker for KDE since the 2.x days.
If that's what they want who am I to tell them no? The point of open software is to be what the user wants. Why is any particular opinion more correct than another within a group that prides itself on giving users choice.
If KColorPicker isn't someone's cup of tea, there is nothing stopping anyone from changing that default out. The color picker that appears is a user setting.
They're giving you shit about complaining about a nice and working color picker for no reason except that somebody made something similar quite a while ago. Nobody cares about your color picker, you are the only one bringing it up.
If it's such a problem for you, and you are obviously a colour picker expert, why don't you make KDE a new colour picker. I'm sure the community would appreciate a new and innovative colour picker, if it's genuinely better than the Windows style one.