I’m no color widget expert but here’s what I’ve noticed. Almost all color widgets screenshots you posted above have their own color intensity (saturation and value) slider isolated separately from circle/rectangle which is our color hue.
Whereas the triangle one we see on GTK doesn’t really need additional sliders because the unique color (hue) is the circle enclosing the triangle and each side of the triangle manipulates color intensity.
The Gtk triangle version has a disguised slider lol.
I don’t know if that what they’re fan about it.
The triangle has a weird way to manipulate saturation: you need to follow a curve (someway a ‘parabola’) inside of it…
Anyway, I think there isn’t a consensus. 
Finally back on this project.
What do you think? What is the best?
The button on the top-right corner is the EyeDropper (without icon 
)
I still need to place somewhere the Hex entry and the numeric entries for each color component. Any suggestions here?
PS: Yes, I’ll fix the Hue vertical slider
What about this layout?
packing vertical vs horizontal hmm… I think your 2nd design would scale a lot better on widescreen monitors 16:9
How about adding a palette too at the empty place?
Even better how about dynamically generated color palette from the hex value?
javascript - Create Complementary, Triad, and Monochromatic Color palette from single Hex Color - Stack Overflow
