Most User Friendly Color Picker

I'm designing a website, and I need to allow the user to change the color of some elements. I will have to implement a color picker. What kind of color picker is the most user friendly, and looks best?

I've got four different kinds so far, but if you have another better one, please let me know.

I'm fully flexible with how the design looks.

#1: Square Color Picker
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#2: Color Wheel Color Picker
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#3: Color Wheel - Square Color Picker
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#4: Color Wheel - Triangle Color Picker
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